Welcome to BC..
Well you can try for starters replacing your host file
and few free but very good proggies like, SpywareBlaster can encrypt and create a backups of your HOSTS file.
WinPatrol 8.1 will allow you to lock your HOSTS file and will monitor changes.
SpyBot - Search & Destroy has an option to "lock" the HOSTS file.
Here are the links to Host file SpywareBlaster WinPatrol Spybot-S&D
Please download those programs and Host file, update them, disconnect from the internet and run those programs preferably in safe mode..
If problem still presists, read (carefully) our tutorial on HijackThis and post the log..
When one of our Hijackthis guru's find the time, he/she will be glad to help..
Down in the bayou, Bubba called an attorney and asked, "Is it true they're suin' the cigarette companies for causing people to get cancer?
"Sure is Bubba. But why you asking?"
"Cause what I want to know is, I was thinking, can I sue Budweiser for all them ugly women I've slept with?"