change your operating system completely! most viruses / spyware / adware is written for windows. change operating systems, it won't run on your computer.
if it's possible, when you first get your computer you need to start taking secuirty measures right away. my sister learnt the hardway dispite having pleanty of secuirty there's still stuff she can't get rid of.
when installing these these programs, it's good to make sure you're computer is clean you can get a free virus scan from http://www.pandasoftware.com/actives..._principal.htm
there's pleanty of products out there to keep your system clean. try and stick to the known names, the price may be a bit higher, but it's usually worth it. compromising secuirty to save a dollar isn't the way to go.