Scan for malware:
1. Use safe mode with networking to download, install, and update Malwarebytes. Then do a full system scan.
2. Do the same with SuperAntiSpyware http://www.malwarebytes.org/mbam.php http://www.superantispyware.com/download.html3.
3. Disable your current anti-virus.
4. Download, install, and update Avira Anti-Vir. Do a full system scan to double check. Avira is a real time, live updating AV.
5. Use CCleaner to repair any registry damage.
6. Re-enable your current anti-virus
7. Stop using the Windows firewall, as it protects in only one direction. use Outpost or ZoneAlarm (without the toolbar.)
8. Get SP3 and all subsequent Updates.