Installed Windows 7 RC 32-bit yesterday on an Optiplex 745. I've right-clicked on several particular folders in My Documents, clicked Advanced, and checked the Encrypt tab. Immediately Windows7 prompts me to backup my certificate which I do. I have no troubles opening the files (xlsx, xls, doc, docx, pdfs, and so on.) When I reboot and come back the next day (today), I can no longer open any of the encrypted files. I'll receive error messages from Excel stating "Excel cannot open the file because the file format or file extension is not valid. Verify that the file has not been corrupted and that the file extension matches the format of the file." If I turn off encryption, I still get the same error message.