K7N2-ILSR reboots, cannot reinstall XP, video gone

Question

Well, since I built my machine 3 months ago, I've been having problems with it, but because I really didn't know what was wrong with it, I could not narrow it down to anything.  
What happened was that my computer would reboot on its on whenever.  It would reboot especially when I'm playing games like NBA Live 2003, Warcraft III, etc. and if it didn't reboot, it would kick me out of the system.  
At first we thought it was a PSU problem, but after we replaced it and had the same problem, we figured otherwise.  
I have
K7N2G-ILSR board
Athlon XP 2500+ Barton
2x Infineon 512 DDR
WD120 /8mb cache
WD80
onboard sound, video, nic
burner, dvd, nic
BIOS should be newest stable version.
After reformatting over and over again, it was evident the problem was not software based.
I even brought it into FutureShop (Canada's #1 computing franchise) and their techs couldn't figure it out.  We ran Troubleshooter on it and all the hardware passed the tests.
They instead downclocked the FSB to 133 from 166 (default) which then lowered my CPU speed to 1900+.  The reboots did not come as often, but they did still occured.
So I decided to reformat again and reload XP but that was when the problems occured.  The first 5-6 times, I got different errors from Windows (boot off CD) stating that there are errors and that it did not want to damage my computer further (a different error every time, but one of them was irql_none_or_equal_to of something to that effect.
Since I never had this problem prior to visiting FS, I decided to reset my bios to default settings.  After that, every time I tried to load Windows, it would give me read errors on the CDs.  I tried different CDs on different drives, and still I got the same read errors - stating that it cannot copy certain files.
Today, I decided to try something new and set to high performance settings.  Once I did that, the video turned off, and I got a blank screen ever since.  Turning on the comp does not turn on the monitor any more, and the D-bracket is stuck at "Initializing Video Interface".
Sorry for the long post, but I just wanted to be thorough.
My questions -
1) Are the default settings to the motherboard good to go?  Shouldn't I be able to run my system smoothly with them?
2) Does changing FSB to 133 from 166 make a diff?  Why does it lower my CPU clock?  What should I change to make the CPU back up?
3) How do I get back to having video?
4) Does this sound like a motherboard problem?  I've tested just about everything: hdd, RAM, PSU - i don't know what else it could be.
5) What suggestinons do you have?
6) Help?  
Thanks for your input

Answer 1

I'm having the exact same problem, completely random reboots, I've pretty much nailed it down to a bad stick of RAM now, I tested with memtest86, after errors I put a single stick into the single mode dimm, crashed almost immediately after loading winxp, I switched modules, and it's been running smooth ever since (going on a day, but typically I would have seen a crash by now).  It's probably not PSU, I bought a new case/psu because that's what I also thought it was, but the new psu actually sags on a few values (3.3=3.0, etc etc) and it still maintains fine, why it sags like that I wouldn't know, it's a 420W psu, while my old one (which had rock solid voltages) was 300W....oh well...
I'm fairly confident either my RAM was incompatible with my board or the RAM has just gone bad somehow... (I've had crashes ever since I installed the board, but with strange frequencies in occurance (eg, it ran great for the first 2-3 weeks)