Here is a link that should help you understand the difference:
I have both XP Home and XP Pro, but have not used XP Media Center Edition.
The difference in Home and Pro is neglegible. Pro simply adds some options that are better for businesses; mainly better security for networking.
- COOLER MASTER Wave Master TAC-T01-E1C Silver Case
- DFI LanpartyUT nF4 Ultra-D (BIOS = latest)
- AMD Athlon 64 X2 4800+ Toledo 1GHz HT 2 x 1MB L2 Cache
- OCZ 2GB (2 X 1024) DDR (500) PC-4000 EL Gold Gamer Ext. XTC (OCZ5002048ELGEGXT-K)
- OCZ PowerStream OCZ520ADJSLI ATX, BTX, EPS12V 520W
- XFX Geforce 7900 GTX 512MB (665/1630)
- HITACHI Deskstar 7K80 80GB 3.5\" SATA 3.0Gb/s x 2 (RAID)