Pop-up blocker? turn it on
Or maybe sometime, u accidently clicked somewhere which is those annoying advertise, so they r now keeping open IE with thier website now
Try go to internet option, and insert
http://www.google.com as homepage
See if it's fix or not
And scan the virus
I used to have this too, and it's really really annoying...
Or maybe u try to find some strange Name.exe in Windows Task Manager
Do this:
Ctrl+Alt+Del
Click Processes Tab
Click User Name Tab, this will list the program by ur username
Close every .exe (Only ur User Name, not LOCAL SERVICE, NETWORK SERVICE or SYSTEM) except:
-explorer.exe (Desktop)
-taskmgr.exe (Windows Task Manager)
**
iexplore.exe is Internet Explorer
msnmsgr.exe is Windows Live Messenger
Try to find strange name and click End Process then click Yes

:ps: Hope it fix