Download these programs.
Smitrem
AdawareSE
Ewido
Update Adaware and Ewido.
Then boot to safemode (tap f8 on startup).
Once in safemode, run Hijackthis and check these lines.
R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Search Page = http://red.clientapps.yahoo.com/cus...//www.yahoo.com
O4 - HKLM\..\Run: [P.S.Guard] C:\Program Files\P.S.Guard\PSGuard.exe
Close all open windows and hit "Fix checked".
Open the Smitrem folder and double-click
RunThis.bat. Wait for disc cleanup to finish, it may take a while.
Then run a full scan with Adaware.
Then a full scan with Ewido.
Then boot back to normal mode and post a new Hijackthis log.