Yuriman, I think that the poor guy has spent enough already. I think the Fortrons are great PSUs as well, but he should be just fine with an Antec for now
OK, madillo, let's recap.
You've tried alternates of the following:
Motherboard (PC chips and gigabyte)
CPU (2500+ and 3200+)
Memory (2 different brands)
PSU (old PSU and new Antec)
You've had the same problem (blue screen) every time you've tried to run the machine at stock speeds.
Unless you have 2 bad motherboards as you suspect (possible), the only things left are your video card or HDD since the CPU and memory have performed well in other machines (correct?). I tend to doubt the HDD, but you might want to boot into safe mode and run checkdisk just for fun. If checkdisk runs OK, just get a $20 16 or 32 meg agp video card to test things out. If you still get blue screens with it, you can then buy a new motherboard with confidence.
You will eventually isolate and resolve this issue. Keep at it, my friend.