|okay a few things to try.|
Download Spybot Search and destroy from safernetworks - google it
Malware bytes Anti malware. Free edition is good
Download Kaspersky Anti Root Kit, just to scan for rootkit problems
Install, update and run all 3 programs. Spybot has a host blocking function that
sets lots of known bad sites web page address's to 127.0.0.0 in your hostsfile then alows you to lock it. Also the imunisation function is very good at keeping most web crap at bay.
Malwarebytes is a good one to have running in taskbar. Not as annoying as the spybot tea timer.
Kaspersky rootkit remover is great and free. Removed DOS/Aluron A rootkit from my system, when all else failed.
Microsoft Security Essentials is allright but stops any keygens/memory pokers
from running (if you use that kind of thing)
Hope this helps get you moving again.
One last thing, try running things in windows safemode if you have a prob that won't go. Helps by only loading what is needed.