Possible caues:

1) win7 is at fault for whatever reason
2) upper&lower filters issue
3) drive is kaput
4) SATA connection is loose or at fault

Not, knowing can be maddening, however since win7 is only released this week if not the RC version, then a problem is brewing or becomes known. Some of the same issues with Vista/XP still appear with win7 as filter, google for fix. Yes, a drive will go belly up if bad power or a hit was done asyou stated you had to physically open drive. While SATA connections can be a cause, if it clicks or seats well, it shouldn't be it.

I suggest you get the Ubuntu .ISO file and burn to a CD and see if that works for a boot-up of the LIVE CD version. If it works OK, then the problems lies in s/w not h/w. Google for live Linux version of Ubuntu. If you're using win7 as a RC version, maybe the retail/upgrade version if glitch free, but you gave no acct. of what win7 you're using.

tada -----Willy Happy