dude, download the administrative version of service pack 1.... (or sp2 for that matter) it wont matter whether your copy is legit or not if you use the administrative version in most cases, unless you have a really messed up common CD key...
also, yeah i wouldnt leave the hard drive loose like that.... there HAS to be something, a sliding devide or even 1 hole so it kinda stays in place...
what i strongly recommend is buying a removable HD tray, then you can leave it in the 5'4 bay with your optical drives and it will be even safer and cooler than in its designated position.