You can use Windows Media Player to slow down tunes without pitch change, it’s easy to set up. I have the latest WMP version 10 running on VIAO laptop with XP. And it’s free.
Open WMP and goto the View menu;enhancements; and click on speed settings. It works after you have ripped a copy of the tune (say from a CD) to the WMP library which is really simple to do on WMP. But not if you are playing a CD directly on your computer, at least I have not found how to do this.
You can take tunes from the library and add them to a playlist that has only the tunes you want to practice and can play the playlist alone and can loop it. Pretty good organization.