Hi,
Is it possible to do the following:

take a hard drive with win xp already installed on one machine and then put it into another machine with a different motherboard

would i have to do a repair INSTALLATION?

check your specs first before you do anything and it depends on what type of computer/motherboard you have. If its going into a computer with the same hardware and specs then yes. But if its a faster or slower mother board or a different video card, then it may come up wrong. I've EXPERIMENTED with this before and put an old hard drive in an old computer and a couple of things happened, the video resoulution and color was jacked up and I couldn't fix it without re-installing the OS and a couple of times it has thrown a blue screen, and I've found out that if its not a blue screen for installing windows, setting or you dont do it, most of the time its BAD. So long story short, I wouldn't the motherboard is different different specs also, but wouldnt a recovery/repair install of windows work so rather than changing the hard drives i also should install xp on the new hard drive but only as a repair so i get to keep the filesyou may just have to create a back up, because a system restore wouldn't do anything on a new computer, because THERES nothing to restore. Everythings on the harddrive already. If you have Ghost, or could get you hand on a copy, that would be the easiest thing, and it would probably take you about 5-7 minutes or lessRepair Install of XP

I suggest reading it thoroughly paying special attention to the warnings and printing out a copy for reference...
Done properly the machine will now boot with your data and Apps intact...
Done improperly all your data will be gone but you will have a fresh install of XP.thanks patio thats a handy guideThank Michael STEVENS....
Best of Luck.