I will be assuming that people are running either windows 2k or xp in this tip:

Download these tools and install them:
AdAware => http://www.webattack.com/download/dladaware.shtml
CoolWebShredder => http://www.spychecker.com/program/coolwebshredder.html
SpyBot => http://www.snapfiles.com/download/dlspybot.html
Spyware Blaster => http://www.javacoolsoftware.com/sbdownload.html
Stinger => http://vil.nai.com/vil/stinger
ToolBar Cop => http://www.mvps.org/sramesh2k/toolbarcop.htm
After that Follow these Instructions:

1. First turn Off your System Restore
2. Boot into safemode and Login as Administrator
3. Run the AntiVirus tool and delete all viruses it found
4. Run the Spyware Removal tools and delete everything they detect
5. Then goto C:\Documents and Settings\[username]\Local Settings\Temp and delete all files present here
6. Goto C:\Documents and Settings\[username]\Local Settings\Temporary Internet Files, and delete the folder of ContentIE
7. Goto C:\Documents and Settings\[username]\Cookies, and delete all cookies present here.
8. Reboot back in Normal Mode and check if problems are gone
9. After making sure that every junk stuff is deleted, and System is Clean, Turn On the System Restore again !!!
10. If your computer is fixed then Great, otherwise run the Hijakcthis scan, and post the LOG file here -- (link for hijackthis)