Sounds like you have some nasty spyware. XD There are tons of Anti-Spyware programs on the internet, Ad Aware is popular, so is SpyBot. I like Spyware Doctor though, but you gotta pay which is bullshit. Yea those programs should get rid of most/all of the garbage on your computer.
You might want to clean out your registry too. If you've had your computer for a while, the registry tends to build up for every program you install, the registries can also get corrupted and slow the comp like a mofo. Get a registry cleaner to clean it up. RegCure, RegSeeker are good bets.
AdAware
BufferZone (30 day trial)
SpyBot
RegSeeker