I can no longer decrypt certain files. The only cause I can think of is that I changed the Windows 7 product ID. I've tried changing back the Product ID to the original. Doing so didn't help. I'd be most grateful for any remedy.

Hi, Thanks for the post. Which type of encryption do you use? Based on my understanding, to change the Product ID cannot affect this. If you are using EFS, I assume that the certificate which is used for decryption is missing. If you have the backup or recovery agent, please import them into this computer, then try to refer to the following article to remove encryption. http://support.microsoft.com/kb/308993 Note: this also applies to Windows 7. Regards, Juke TechNet Subscriber Support in forum If you have any feedback on our support, please contact tnmff@microsoft.com. Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Hi Juke, thanks. Sorry not to have said - the encryption system is EFS. I should mention that most of the green coloured files do decrypt, it's just some of them (those before a certain date) that don't. regards Clive

Hi, Based on my understanding, the encrypted files cannot get back if you do not have proper certificate which is used for decryption. Please open Cetificate Manager to check your certificate status used for EFS in the personal category. I suspect that the certificate is already expired so that this issue happened. Also, you may try to contact the Data Recovery Company for assistance on this issue. Thanks for your unerstanding. Regards, Juke TechNet Subscriber Support in forum If you have any feedback on our support, please contact tnmff@microsoft.com. Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Hi Juke, thanks. According to Cert Manager the two certficates in the Personal Folder having EFS as their 'Inteded Purpose' have 100 years or so to go before expiry. The O/S version is Ultimate - is Bit Locler more reliable in some sense than EFS? regards Clive

Hi, They are different encryption type. Bitlocker will encrypt the whole volume, but EFS can encrypt a single file. If you need to encrypt a volume, you can use Bitlocker. BitLocker Drive Encryption Overview http://technet.microsoft.com/en-us/library/cc732774.aspx Regards, Juke TechNet Subscriber Support in forum If you have any feedback on our support, please contact tnmff@microsoft.com. Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Hi Juke, Thank you – you confirm the understanding I had of the difference between the two encryption types. Addressing the question which of the two types is more reliable, would you say both are equally reliable? I mean no one besides me has encountered a case where some files encrypted by EFS are decipherable but some are no longer decipherable? Regards De sales

Hi, If I have to say it, I think all of them are reliable. I assume your issue is caused by the certificate which is used for encrypting those files is missing so that you cannot decrypt them again. You need to check the thumbnail of certificate used for those files to see whether it matchs the exsiting certificates in personal catagory. Also, please back up the certificate in a safe place or set up a recorvery agent in the future. Regards, Juke TechNet Subscriber Support in forum If you have any feedback on our support, please contact tnmff@microsoft.com. Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Hi, Any update? Have you checked the thumbprint? Regards, Juke TechNet Subscriber Support in forum If you have any feedback on our support, please contact tnmff@microsoft.com. Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread. ”

Sorry for the delay in replying. Quote from penultimate email: You need to check the thumbnail of certificate used for those files to see whether it matchs the exsiting certificates in personal catagory. Where does one unearth the thumbnail of the certificate used to encrypt the file so one can see whether it matches the certificates existing in the personal category? regards Clive

Hi, You may refer to the following article to check the thumbprint. Using Efsinfo.exe to determine information about encrypted files http://support.microsoft.com/kb/243026 Regards, Juke TechNet Subscriber Support in forum If you have any feedback on our support, please contact tnmff@microsoft.com. Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Hi Juke, thank you. Just like you surmised. No certificate with a thumbnail matching the file's thumbnail. [1] I recall you said changing the Product ID should not affect EFS. But reinstalling Windows 7 (which I also did) would of course have done so? [2] But I used the Xfer Wizard. Doesn't the Xfer wizard preserve all necessary such certificates? Regards Clive

Hi, Of course, These certificates would be lost if you reinstall the Windows 7. What is the Xfer Wizard? I guess you mean Windows Easy Transfer. If so, I would like to advise this software do not save the certificates. This tool is used for transferring your personal files. http://windows.microsoft.com/en-US/windows7/products/features/windows-easy-transfer Regards, Juke TechNet Subscriber Support in forum If you have any feedback on our support, please contact tnmff@microsoft.com. Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Hi, Do you have any other concern? Please feel free to let me know. Regards, Juke TechNet Subscriber Support in forum If you have any feedback on our support, please contact tnmff@microsoft.com. Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread. ”

Hi, Since you have already reinstalled Windows 7, so I will mark my reply as "Answered". If you have further question about this, please feel free to let me know. You may also choose to unmark this thread. Thanks for your understanding. Regards, Juke TechNet Subscriber Support in forum If you have any feedback on our support, please contact tnmff@microsoft.com.Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Sorry again for my delay in replying. Regarding my misnaming Windows Easy Transfer - you guessed correctly - sorry. Thank you for the astonishing news that even though one has used Easy Transfer (ET) (a Wizard that assures Joe User that all files selected - including files whose names are coloured green, ie files so important to Joe User he has encrypted them) any files coloured green - for all their having been successfully transferred - will be unusable. I appreciate good practice requires that one export certificates, but on first encountering encryption all that is needed is to tick a box - one is not alerted to a need to do anything else if the files are to remain unencryptable at a later stage - specifically at the stage of using ET. Mightn't it be worth redesigning ET slightly so that if files transferred by ET are encrypted files EITHER the Wizard includes in the transfer the certificates needed for the files' decryption OR AT LEAST FAIR WARNING IS GIVEN that notwithstanding the encrypted files having been transferred it won't be possible to decrypt them because the certificates are not being transferred? ET as it stands is a trap for unwary players 'n'est ce pas'? Or am I missing something? Luckily - the encryption having been something of a trial run - I had made a copy of the files before encrypting them. The copies were transferred so the files have remained mostly available. Thank you for your patient and most helpful replies - I agree with your marking of the answers. (I wonder if it may not be worth including this reply as an answer as well.) yours sincerely Clive

Hi, Thanks for your feedback. I think it may be necessary to mark your latest reply as "Answered". This could benefit the other viewers. Thanks. Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.