I don't know that the copy protection is the problem, for certain. I know diablo2 runs fine with my kenwood 72X, Win2k/98, original and backup. I know I've seen issues on the official FAQ at blizzard about certain (don't remember which) drives having problems with diablo2, and the usual 'update your drivers/firmware; you're sucking really bad if that doesn't fix it' answers. It is possible to 'crack' the game so the protection gets thrown out the door, and you run completely off the hard drive; there's about 4 or 5 different ways of doing this.
Possibly it could be the motherboard not liking the drive. You might, if you have access, plug the drive into another computer and try running diablo2.