Hi Jenni, and
As Joudi said, we need to know some more details:
Which version of Windows are you running (98, ME, XP, etc)?
Which software are you using to download the music files?
What is the capacity of your hard drive, and how full is it?
Just to confirm, you are saying the more music that is stored on your hard drive, the slower the PC gets? What happened when you re-installed Windows? Did you also put back any music files you had previously downloaded, and what was it like at that stage?
Which anti virus system are you running, and what do you mean by "it doesn't seem to be doing much"? Is it regularly updated, and have you done a complete system virus scan?
One more! Are you running any sort of spyware / adware scanner / remover, such as Ad Aware, or Spybot? If not, it might help to do so, as sometimes, spyware can clog up a system, although this may not be connected to your particular problem. Links below.
Sorry for all the questions, but hopefully they may help one of our techies solve your problem.
Ad AwareSpybot S&DSpyware Blaster