I believe the probe method is to determine RAM size. It's antiquated and is available just for use on really old RAM types.
So far it sounds like it's ending up to be the motherboard or PSU. Often in real-world scenarios they'll bug things out but never do doing specific hardware tests. A single bit corruption is a common symptom from them. Again, you'll want to finish all the aforementioned stuff like providing that HWInfo log and turning on Driver Verifier.
As for figuring out the bugchecks, understand that it takes a good bit of knowledge to properly diagnose these kinds of things, and even then you can only go so far to determine if it's software-derived (in which case you can find exact cause) or hardware-derived (where you can only make an educated guess what hardware it is). 0x50 bugchecks are one of the most common bugchecks of all and can come from nearly anything so unless you whip out a kernel debugger and start cracking on a kernel or full dump or two, you most likely won't be able to determine cause.
Driver Verifier can at least greatly assist in determining if this is software-derived or otherwise. Provide us any new crashdumps after you turn it on. Remember which checks not to select.