Uh oh! You got spyware! And if i had to suggest something, get some anti-spyware programs quick!
Although the pop ups probably aren't that harmful [damn annoying though] they might lead to other little worms that might eventually take apart your computer and even steal your passwords [phising]
Is your internet explorer updated? The new ones tend to have pop up blockers, but sometimes even they fail to block anything, i suggest trying the program ' Lavasoft Ad-Aware SE personal' which can be downloaded from www.download.com . If that still doesn't solve your problems try an extra anti-spyware program or too [but be careful when downloading].
If your ad problems are still there, it could be a virus, scan your computer with some anti-virus stuff, and see if you can find anything.
Finally, if the ads are still going crazy, and you've tried everything, re-format your computer, but be careful when backing up some files, as they may be spyware infested.
Anyways, in the future, always be careful of what sites you visit, and of what you download. Mozilla is the favoured browser, so try to avoid IE.
Hope it helps at all!