TRY THIS FIRST:
Restart your computer and press F8 just after it starts up again.
This will give you startup options.
Choose "Safe Mode with Networking"
Once you are in (icons will look big and weird) get on the net and go to
www.malwarebytes.org
On the left hand side, choose the blue Download Free Version.
Save to desktop and double click to install. There will be a moment or two when it appears to not be there - but finally the scan window will open. Short Scan will be selected. Leave it at that and start the scan. It will clean out all kinds of crap and viruses. It is one of my basic cleanup tools.
The other is Spybot Search and Destroy - but do Malware first.
This could take a couple of hours total, but will save you the drive and money!