If you manage to set up Motherboard Monitor up correct, (not a jab, just sometimes I have problems with it
) not only will it tell you if all you need to know about your fans, but it'll also help diagnose a failing power supply.
The high-pitched whine though, certainly seems to me to indicate it's a fan and by extension an overheating problem. Hard drives, and I've only had a few lock up on me over the years, sounds more like a god-awful grinding rather than a high-pitched whine.
Just because it hasn't been mentioned... Have you moved the tower around a bit lately? There was a fellow at work, an instructor on campus, who moved his office around, and being none to careful with the tower managed to knock his motherboard loose, which created an odd little short circuit that completely locked up the pc from time to time. He told the computer services guy that he'd been 'fixing' the problem by giving the tower a good shake....