Have you tried logging in to safemode? To get in to safemode gently tap F8 as the computer reboots. When you see the menu, select safemode with networking.
Install, update and run Malwarebytes. You can get it HERE
. Install, update and run it. If you have problems installing it then try renaming the file before saving it to your desktop. I like renaming it to bgmama. Get rid of what it finds.
Remove what MBAM finds and then install and run ATF Cleaner
(for WINdows XP and 2000 only!). Check the box for select all and then click the button Empty Selected. This will help clear out temp files, cookies and other junk that clutters up Windows.
Next install, update and run SUPERAntiSpyware
. Get rid of what it finds. Finally update and run your antivirus program and get rid of anything that it finds. If you are able to run MBAM and SAS please post the logs in your next response.