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?

The best place to uninstall programs is through Control Panel Add/Remove Programs applet. Though some applications leave some traces behind after uninstalled in the hard disk, but they are harmless to your computer system. If uninstall programs by third-party uninstaller, the system registry files are also deleted along with existing programs which you still want to use.

There are some viruses that attack programs and applications that are needed to remove them.

try to install the programs in safe mode and run them from there and see what developes. You can try to use an online virus/spyware scanner.

Antivirus & Content Security Software | Securing Your Web World: - Trend Micro USA

Tune-Up Tips

both of these have excelent free scanners.

It was an hldrrr trojan which I removed with RegRun. Thanks for your tip