This may be caused by a third-party program (adware, spyware, parasite).
Get AdAware and Spybot and run them both. Keep them up to date.
Dealing with Unwanted Spyware, Parasites, Toolbars and Search Engines
http://mvps.org/winhelp2002/unwanted.htm
If you find this one get the removal tool.
CoolWebSearch - CWS
http://www.spywareinfo.com/articles/cws/
More: Where a removal program is available.
http://www.spywareinfo.com/~merijn/cwschronicles.html
Direct Download: If the site is not available.
http://216.180.252.218/~spywareinfo.com/downloads/tools/cwshredder.zip
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If all fails, then you may have a new variant.
Go to
http://www.spywareinfo.com/downloads.php#det
Download "Hijack This!" [freeware] or download direct (below):
http://www.merijn.org/files/hijackthis.zip
If you get a 404 error or Access denied, try:
http://216.180.252.218/~spywareinfo.com/downloads/tools/hijackthis.zip
Unzip, double-click "HijackThis.exe" and Press "Scan".
When the scan is finished, the "Scan" button will change into a "Save Log"
button.
Click: "Save Log" (generates "hijackthis.log")
Next, HijackThis | Config [button] | Misc Tools [button]
Click: Generate StartupList log [button] (generates "startuplist.txt")
Next, go to the below location:
http://www.spywareinfo.com/forums/
Sign in, then copy and paste both files in your message.
HijackThis Quick Start Help
http://www.tomcoyote.org/hjt/
The Tutorial if you want to know more about the results or the .log file.
http://www.merijn.org/htlogtutorial.html
____________
Henri Leboeuf
Web page:
http://www.generation.net/~hleboeuf/index.htm