It seems like you have a hijacker on board. Here are general malware
removal steps. All steps should be done with updated tools in Safe
1) Scan in Safe Mode with current version (not earlier than 2003)
antivirus using updated definitions.
2) Remove spyware with Spybot Search & Destroy and Ad-aware. These
programs are free, so use them both since they complement each other.
There is a new version of CWShredder from Intermute. I would not
install the other Intermute programs, however. Alternately, there are
CoolWebSearch malware removal steps at SilentRunners.
Be sure to update these programs before running, and it is a good idea
to do virus/spyware scans in Safe Mode. Make sure you are able to see
all hidden files and extensions (View tab in Folder Options).
HijackThis is an excellent tool to discover and disable hijackers, but
it requires expert skill. See below for HijackThis links. A combination
of HijackThis and About:Buster works well in removing the About:Blank
homepage hijacker. Again, this is an expert tool and novices should get
help with it.
3) If you are running Windows ME or XP, you should disable/enable System
Restore because malware will be in the Restore Points. With ME, you
must disable System Restore completely. With XP, you can delete all but
the most recent (presumably clean) System Restore point from the More
Options section of Disk Cleanup (Run>cleanmgr).
4) Make sure you've visited Windows Update and applied all security
patches. Do not install driver updates from Windows Update.