How old is your Windows installation? WinXP needs to be reinstalled about once a year because of all the BS that clogs up its operation. If you are tihnking about upgrading to Win7, don't. Its a whole new OS to learn. You might as well make the jump to Linux (MicroSoft stole most of their new ideas for Win7 from them anyway) as Linux is easier to learn than the new Win7 and is free. Think I'm kidding about Win7? Go try it on somebody else's PC.
As someone mentioned earlier, its best to just go cold turkey on MicroSoft. Go to www.distrowatch.com and download any of a number of Linux OS's that specialize in music, such as 64 Studio, ArtistX, Musix, and/or Ubunto Studio. You will find the equivalent freeware version of your music software already on these OS's.
You can burn a Live CD/DVD to test drive the OS before you install to see if you like it. Just boot from the Live CD/DVD and log in.