win 8 upgrade from 7

Hi there, I have a home built pc with 4 hards drives instead of dual booting i have the following on 3 drives win xp, win 7 win 8 I just preess F 8 for the boot menu and select the drive with the operating system I need.. I installed win 8 from a fresh installed copy of win xp without any problems other than the win xp 32 bit version and it upgrade it to win 8 pro 32 bit. I was wondering...