Virus hijack computer - denies access to safer-networking, SPYBOT; etc

[T1m11]

I think I got something nasty.
The computer now sometimes stalls when I start and have to restart 2 or 3 times before WinXP opens. I can use the internet but very slowly and anything to do with SPYBOT sites are denied.

I always have SPYBOT and Lavasoft Adaware which work for me for years but right now and can't open the existing SPYBOT. I can use Lavasoft but can't update it. I tried uninstall and reinstall SPYBOT. Doesn't work either.

I followed the procedure and back up the registry with ERUNT. However, I can't install HijackThis 2.0.2!!

Please help.

[T1m11]

I did download HijackThis 2.0.2 successfully but when clicking to install it nothing happens.