You have a virus...delete everything on your computer NOW!
On more serious note, try clearing your internet cache, history, cookies, temp files etc.
Hold Ctrl + Shift + Del
Then clear everything that's checked. (You don't have to check anything, it should be checked already).
Same process for Firefox/IE.
To clear Temp files:
Go to start, Run. Type in %temp%
This will being up a folder. Delete everything in this folder. Sometimes some of the files are in use and cannot be deleted. Just leave them.