I see this question has been asked a few times already but without any real solution and the threads seemingly petering out. I am unable to install windows updates, updates to Adobe, updates to AVG and also unable to install HP Support Assistant (error 1601) and other programs (eg .msi) I get the error message "The Windows Installer Service could not be accessed" I have tried many fixes suggested on this forum and many other forums also, including the Windows Standalone Installer service update. I have also tried the many "automatic" fixes (FixIt, Windows Update,) without any success. I am using W7 Home Premium 64bit Thanks for any help! Graham

I suggest you temporarily disable AVG and check the result. If the issue still occurs, try the steps in the following article "The Windows Installer Service Could Not Be Accessed" error message when you install a program in Windows XP http://support.microsoft.com/kb/315353 The steps are also applied in Windows 7.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 Arthur, Thanks for replying. I have tried your suggestion but still no luck. I guess I'm looking at reinstalling Windows7 :-( Oh well.....