Get Ad-Aware and update the reference file. Restart into Safe Mode and run a scan with Ad-Aware. When it shows the list of stuff it finds, make sure they're all checked by right clicking on one of them, and choosing Check All. Continue till it says it deleted everything, and after restarting everything should be fixed.
To get into safe mode you just tap F8 before your Windows screen comes up. If the Windows screen comes up, restart and try to be quicker the next time. On some computers there's only like a half a second time frame that you can hit the F8, so you've got to be quick.