I actually keep spare fans and PS's around just for that. The only thing I Don't keep around evidently is a spare floppy drive... I haven't built a PC with one in it for quite some time... Turns out when one installs 2K or XP and you want to use 3rd party drivers (like to boot off one's raid array) you MUST install them via floppy, there is no way to get it to look for those files on your CD or Network :(
my geeky-ness