There will be a jumper on the h/d marked master. The disk you wish to boot off has to be the master. So un-jumper the current boot disk, actually I can't go on. If you don't know this you shouldn't have your pc open in the first place. And if another person says, go into you pc set up, well......
I assume your are/have installed a bootable O/S on to the second disk too??
ASK a Pro
March 2007