Guys,
Spyware and adware don't install themselves in a nice way that legit programs do. That's why they are called "spyware". They hide!!!! You won't likely see them in the Control Panel Add/Remove programs area.
I would recommend that everyone has free spybot search and destroy and or adware to keep these thieves at bay. They can be a lot more than just annoying. You can have banking passwords and other important data stolen if not careful.

ZoneAlarm is also a good idea if you want to see if a virus or rouge program is trying to acccess the internet while you are doing something else. It can be annoying for a while as every program that goes to the internet will initially be blocked and yo have to ok it. Even updates to programs will initially have to be okayed access.

The way you get these things is to crawl around on web sites that you probably know you should avoid. You know which ones I mean .. Guys!!

The other way is to click links that spam software is teasing you to visit so you get some drugs cheap or show you ways to grow your manhood, etc.

You need to practice safe computing.
Need a updated virus scanning software, spyware remover and if you are on line a lot or have broadband you need some sort of firewall. The firewall can be software or hardware based. Zone Alarm is a good software firewall. If you have a router it will help protect against virus and worm invasions. Unfortunately none of these is fool proof but you would be crazy not to have at least these basics tools to protect your computers. I'm in computer business for over 20 years. Just now learning the pondmiester business. Good Luck.