Hi Mike,
I have a Dell also and and it defiantely sounds like your going to do a reinstall. Here's the Dell support site on what to do. It's basically put the restore CD in and let it do it's thing. Just so you know you'll lose everything you had on the computer and it will be just like when you turned it on for the first time.
http://support.dell.com/support/topi...SRG&l=en&s=dhs
Here's a link to the best antivirus program in the world right now that you may consider getting.
http://www.eset.com/home/home.htm