Black screen

Starting a few days ago, after my computer displays the Windows XP loading screen, the screen goes black. After around 10 minutes, the login screen comes up. I login, and it shows the background image for a while (5 minutes maybe?) with nothing loading, and then all of a sudden it starts loading and everything is good from there. This started happening immediately after I put another hard drive into the computer. I have an old broken TiVo, and I wanted a backup hard drive on this computer, so hooked up the TiVo hard drive, but I hadn't formatted it yet, because I wasn't planning on actually backing it up yet. So it still had TiVo in it. With both hard drives in (the TiVo one set to slave) I booted, got to the point after the Windows XP screen, and from there I buttumed my computer was broken, so I turned it off and removed the TiVo hard drive. I am buttuming the the TiVo hard drive is the culprit here, but how do I get this fixed. My Windows XP CD got scratched, so unfortunately I cannot reinstall, and I really would rather not purchase a new one. Thanks for any help.