I am unable to install programs under my XP-SP2 although I can run quite a number of them. It all started when I noticed that my Sygate and Avast icons in the taskbar had disappeared. The corresponding ashAvast.exe and Smc.exe, the executable modules, were no longer present in their respective directories. I immediately cut off the link to the Web. When I reinstalled these programs, the executable modules did not reappear. The same thing happened with Spybot and Advanced Uninstaller Pro in that their exe modules disappeared. Furthermore, whenever I open Windows Explorer, Word or Excel 2003, Windows Installer starts up and asks for Adobe Acrobat 7.0. I ran msicuu2 version 5.1 to no avail. I used the Add/Remove function in the Control Panel to get rid of Adobe. It asked me for the Install CD. When I inserted it, Windows Installer told me it could not find it. I can access the Web. Would there be a virus? Should I try an online virus scan despite the lack of protection? Any particular site you would recommend?

Have you tried a System Restore to a date before the problem started? Life's more painless for the brainless.

After System Restore, use this multi brand scanner in one utility. Windows XP Cleaning Process with Multi_AV http://pcdid.com/Multi_AV.htm

"Would there be a virus?" Most Likely, because the use of executables and not any one antivirus will remove all virus,malware,etc. Try Trend Micro Housecall http://housecall.trendmicro.com/