OK... this is what I was thinking as I rode back to work this afternoon... I have a Mac mini and three hard drives: i) internal 5400rpm 80Gb SATA ii) external 7200rpm 80Gb USB2 iii) external 7200rpm 400Gb Firewire I'm wondering if it's possible to install Mac OS X on the USB2 drive and have it work quite happily there as my main OS. Will my Intel Mac boot from a USB2 drive? If anything goes wrong will disk repair tools fix USB2 disks? Then I would reformat the internal SATA drive and put on XP or Vista as neither of those will boot from external drives. Then use the 400Gb external Firewire for data (partition a bit as FAT32 and the rest as HFS+). Anyone know if this scenario is likely to work before I muck it all up this evening for nothing. Is it worth it? Will using an OS on a USB2 drive seem horrendously slow?