About 30 mins into Mission 2 the PC freezes hard and the speakers emit a high pitched squeal. This has happened over and over. Not problems with the tutorials or Mission 1.

I had a similar problem on mission 6. PC hard freeze, but a buzz on the speakers rather than a squeal. Only way out was pressing the Big Red Button on the front of the machine. It would occur each time from the saves of that level. Restarted the level, played it slightly differently and it went through fine.