Thi sort of problem often comes here from people who klnow what they're doing with computers and are, as youve said, absolutely stumped.

If anybody else takes an interest (which is usually proportional to the amount of technical detail provided in a question), you'll get theories from A - Z.

A freeze is usually caused by one of the following (in no order of priority):

1 Hardware glitching (perhaps due to arcing, bad joint, poor connector, RAM fault, overheating)

2 Driver clash with Windows Kernel in memory; usually blue screens rather than freezing

3 Corrupt kernel process (rather rare)

4 Disk problems corrupting what is read into memory (but you've run Chkdsk).

You can't rule out mis-building of the PC particularly where power connectors are concerned, or a dropped screw or something like that.

Safe Mode might be a tip or a red herring. The difference between Safe Mode and Normal mode (well there are many), but the main difference is that Windows default drivers are used (like the built in 640x480 video). If it freezes during Safe Mode, then you might be guided toward one of the software reasons I've mentioned other than Windows' default drivers.

But then you probably knew all that.