Downloader999

I installed XP Pro, partitioned my hard drive, then installed XP MC on the new part. When I booted to it I installed/opened Partition Magic and renamed the partition I was on (Media Center) to correspond to the letter it was when I booted to the other partition (Pro). When I restarted it applied the changes and restarted but wouldnt boot to the Media Center partition. Why? Can't I change the drive letter without it screwing up? how do I fix it, or, for future use, change the drive letter without error? Can I change the letter of disc drives (ex/internal) safely?? thanx alot