If by chance you went to a website such as mocospace and caught this nasty virus called "internet security 2010" then I have a solution for you. This virus which runs on an infected website which will send you threats that your computer has been compromised.
Here is a simple solution to fix your computer. First download if possible malware bites. If for some reason your not able to download it because of the virus try to do a system restore earlier point before you caught the virus.
It won't fix it right away because some of the residue from the internet security 2010 or internet security 2009 virus stays on your system file.
Go to download.com and type in malwarebites its a good program thats free to use and will remove this virus from your computer. If not your computer will continue to run slow and you will get tons of pop ups.
Hope all works well and safe surfing.