Some spyware are not very smart, they put their name on these ads. I know zango used to do that and say "this ad brought to you by zango" or something along those lines. When you get popups do you see anything like that?
If not...
Do "ctrl alt del" once and look at the processes that are running. If there's anything you don't recognize, do a search for it. If I knew what you had I might be able to help.
Do you have any new icons on your desktop? tray? new toolbar?
Click on "run" then "search" and "all files and folders" and search for "cws" without the quotes. If you got infected with CoolWebSearch, it's a nasty one but the best tool to remove it is free.
IF it lets you download it.
Missie