After installing Internet Explorer 9 things got weird. For instance, when clicking on a Google search result IE9 redirects some place else, among it porno sites. I went back to version 8, everything fine again.

Seems IE9 has serious security issues.

Have you scanned?

Site: Microsoft Security Essentials:

http://www.microsoft.com/en-us/security_essentials/default.aspx

Methinks it would be a good idea.

Would also recommend Microsoft Malicious Software Removal Tool, especially before downloading any programs:

http://www.microsoft.com/downloads/en/details.aspx?familyid=ad724ae0-e72d-4f54-9ab3-75b8eb148356&displaylang=en

I am using Malwarebytes in combination with AVG. Never gave me a problem. But I will try your suggestions. Thanks.

It seemed that the Windows Security Center (http://windows.microsoft.com/en-US/windows-vista/Using-Windows-Security-Center) was disabled and could not be turned on again. Probably a virus after all. That's odd because neither AVG (with Firewall) nor Malwarebytes detected a problem. Anyways, everything finally is ok now after a long recovery procedure using a tricky command-line program called combofix (http://www.bleepingcomputer.com/download/anti-virus/combofix). It's definitely a program I want to keep.

While the problems actually occurred RIGHT AFTER the installation of Windows 7 Service Pack 1 together with IE9 I think my initial conclusion was a bit premature and I want to ask a moderator to close the thread.

Thanks.

another useful tool is HijackThis (http://free.antivirus.com/hijackthis/) it looks in a lot of places that standard anti-virus miss

Thread re-opened.

I agree. HijackThis is one of the best tools available.

Actually, I just spent the past 12 hours on a friends pc that was hanging. After going through and fixing everything I used Hijack This to remove about 16 items - all browser related.

PC works great. Folks think I'm downright handy at this.:rolleyes::D

They're paying the tab on the memory upgrade sticks for my pcs:)