Ok parasiteware stinks!
I have spent most of the day fighting with a computer that is infected with Parasite software.
Parasite software is usually installed sneakily onto your computer under the pretense of providing some service to you. Usually these offer to provide a cool search bar in your browser, Sync your computer clock, or accellerate your browsing. In reality the software often watches where you browse, then presents nasty pop up ads. Usually the software is difficult to uninstall, and is next to useless to the user.
This software often is totaly legal as the user either pressed a button saying that they wanted to install it, or didn't read the license agreement for another piece of software that they where installing and that license authorized installation. It would be nice to legislate this stuff away, but doing so would put a burden on legit software producers. You bought it even if it was a lemon.
If you don't know anything about buying a car, take somebody who does when you go shopping for one. The same goes for software. Check with somebody who knows computers before making a deal with a pop-up ad.
A good website I found today on this topic was doxdesk.com
If you find yourself recieving pop up ads when you visit civilized websites such as "google.com" or "fingertoe.com", then most likely you are infected with something. You computer is making those pop-ups, not the website.
If you notice that your homepage changes all of the time, you are most definately infected.
Anyway, Even if you are not infected, I suggest you take preventitive measures. I trust myself to avoid this stuff, but my wife and daughter use my machine as well, so I would rather be safe than sorry! Here are my favorite precautions. In order from the nerdiest to the un-nerdiest
1. Run linux - not enough people run linux, so it is not economicaly effiecient to exploit. If you are not nerdy enough to do linux, perhaps I could interest you in a Mac?
2, Run Mozilla. I use firefox . It is much nicer than Internet explorer, and doesn't have nearly hijackers written for it. Firefox has pop-up blocking turned on by default. I love the tabbed browseing feature. I also love the mouse gestures extension. Anyway if you switch, you will not ever want to run IE again. Plus you will not risk being infected by this stuff.
3. Download free software to combat the problem. Don't install from one of those pop-up ads though. Those include parasite-ware themselves. Try Spybot to remove this stuff. There are lots of other options available as well. The doxdesk website mentioned above covers them.
Also, if you are an unsophisticated computer user.. (Many people happily admit they are.) Please, Please, keep your Antivirus software paid up... If you don't want to pay, use AVG's free edition