I've made inumerable errors. I installed XP on a harddrive that had 2000 Pro on it, without creating a partition. I need to reformat and start alll over again, but can't seem to find a way to reformat. I try and get an error message that something else is in use and can't reformat. In bios I have it set for CD boot, but when I put the XP CD in it doesn't take me to a prompt. Any ideas?
When booting from the XP CD, the software should ask you where to install it. In that screen, you should see the partions available listed. You should be able to delete the partition, effectively forcing you to re-partition and implied re-format.
If you are having troubles booting from CD, then there is something else at work. Does your system give you a message saying "Press any key to boot from CD..." or something to that effect? If so, you need to tap a key to get into the OS and boot from there.
If this doesn't work, you may need to go to another computer, and make boot floppies. I know you can do that for 2000; I am not sure (but betting you can!) do it for XP. Look for a folder called BootDisks or the like on the root level of the CD-ROM. There should be a utility and some image files.