Virus Busting

While using limewire I searched for a song and found it. While the first download stopped at 53% I looked for another copy of it.
I saw one right away, and clicked it not realizing that the file was absolutely to small to be an mp3 file it was only like 149kb.
And maybe 15 minutes later. Norton Antivirus Alerts me that I have a
"w32.spybot.worm" infecting my computer.

I don't know what to do or how to remove this worm from my computer, but I also realized that the longer I wait, the more it kills my hard drive. I noticed that when I reboot my computer, its memory keeps reducing. Just this morning it had 120 gb of memory, now it only has 80gb.

I know it's a lot to read but any assistance in this situation would be greatly appreciated and somehow I will find a way to reward those who help.
Thank you all in advance

Jam it back in, in the dark.

Well it's probably not killing my hard drive but it's certainly filling it up with so much stuff that it is using up a lot of memory. At least that's what I think it's doing.

There's nowhere I can't reach.

Yeah, well Norton already came preloaded into my computer.
I didn't download it myself, I would have downloaded McAffee but I was told by my friend that the two tend to clash a lot.

And also, I would start over but I have windows media center. And I don't have the CD for it. Good thing is that I can get the Windows Vista Premium for my computer when it comes out. Any thoughts if that would help me out with my problem or would it just follow up on that too?

This thing is sticky, and I don't like it. I don't appreciate it.

Not exactly sure on my firewall.
But for some reason, even though my computer was inactive on downloading anything I only have 42.3 gbs on my computer now. I really don't know what I have to do somehow get rid of this problem so straight forward advice would be appreciated.

How ya doing, buddy?