Computer needs to be completely erased and reinstalled with windows XP, major virus & spyware is

So our computer is completely overran with tons of spyware and a virus that has completely taken over. We pay for high speed internet and no joke it is 50x slower then AOL. When you do a search on yahoo for anything ex: cats then click on the one you want to read it will take me to an advertising site rather then the site i intended to go to then it is impossible to get out, we got norton internet security which helped it alot but it still has something and is getting worse and worse i know its about to crash. My IT guy at work says to wipe the hard drive and reinstall windows, I have a newer compaq comp. got it in 05 dont have a ton of crap/stuff on there storage isnt an issue. It didnt come with a windows CD to reinstall, he told me that you do it yourself now and go burn the windows to a cd yourself then reinstall it. My question is how do I wipe the hard drive?I am good on computers and can do the reinstallation with no problem at all but wiping the hard drive? Any tips to help me?

Computer needs to be completely erased and reinstalled with windows XP, major virus %26 spyware issues...?antivirus scan

First, I'm afraid you will have to get hold of a Windows CD or some kind of recovery CD that sets your computer back to factory settings. Try getting one from the place where you bought your computer from, they should give it to you. If not, download an ISO of your operating system from thepiratebay.org (technically illegal, but since you already have the operating system you are entitled to the CD of it, and you're not going to get caught) and burn it to a CD/DVD using a program such as Nero, Cyberlink Power2Go or MagicISO (this one is free, just google it).