I hate to post huge, long tech problem as my first post on a board, but I'm at my wit's end. Here's hoping this is in the right forum.

The system is about 3 months old, it's from an online builder.

Specs are:

Pentium D Dual Core
Asus P5ND2-SLI Deluxe mobo
1 x Geforce 7800 GT
1 gig of Supertalent at 667MHz (single stick)
Soundblaster Audigy 2 (added by me)
Hauppauge PVR-150 (added by me)
2 x Western Digital 200GB SATA II hard drives
Lite-On 16X DVD+/-RW
Win XP Pro (updated)

Here's a history of the problem.

At first, all was fine, except I would get occasional USB mouse problems where my cursor would disappear and I would have to unplug/replug the mouse.

Then about 2 weeks ago I was playing Oblivion and kept freezing and having to hard restart. When I did, the machine would boot in 800x600 with 4 colors, and no drivers loaded. I'd reinstall drivers and the next crash would do the same thing. I was also getting intermittant BSODs that referred to nv4_disp.dll. Bad Pool Header and Page Fault in Non-Paged Area.

A Memtest gave 20,000 errors in about 5 passes, so the builder sent me a new DIMM. After that the video problems went away, but I was still getting the BSODs. I clean installed XP, and checked my hard drives for errors but they kept happening.

I used the MS debugging tools to look at my minidumps, and they gave me this:

PAGE_FAULT_IN_NONPAGED_AREA (50)
Invalid system memory was referenced. This cannot be protected by try-except,
it must be protected by a Probe. Typically the address is just plain bad or it
is pointing at freed memory.
Arguments:
Arg1: f000e2db, memory referenced.
Arg2: 00000000, value 0 = read operation, 1 = write operation.
Arg3: bf9f206f, If non-zero, the instruction address which referenced the bad memory
address.
Arg4: 00000000, (reserved)

(I don't have the needed six minidumps so I'm just posting that as a quick example)

My builder had me switch motherboard drivers from the NVIDIA Nforce4 SLI edition to one called NVIDIA AMD/Intel x16. They said my board would prefer one or the other, and that if this didn't solve it I should ship it back.

I uninstalled all nvidia drivers through control panel as instructed, rebooted, installed the new drivers and then my video drivers. That didn't seem to go well; I got spammed with "System has recovered from a serious error" after rebooting, and had to click it away about 19 times before I could reinstall drivers.

The BSODs then went away, except that now the machine shuts down randomly every ten hours or so. I say random because it's done it when I was asleep, as well as when burning a DVD and installing a game. After shutdown it won't post back up for about 2 minutes, and always has to be unplugged and then hard reset.

So that's where it is now. My builder will want me to ship it back, but my warranty doesn't cover shipping after 30 days. So I want to do everything I can to make sure it can't be fixed here, but I know just enough to be a danger to myself.

The help I'm looking for is basically, how can I troubleshoot this before giving up and RMAing?

I also want to mention that I have had concerns about my power before (my ex always thought that we had dirty power because she had to RMA 2 separate combos of mobo and processor when building a system in this apartment). My last system also just ... died, stopped booting one day. The board went belly up.

I do have a quality surge protector, but I don't have a UPS. So I'm wondering if my power did this to me, and how I can check that.

I'm also wondering if it's a problem with the hardware I added to the system after receiving it, or if it is the power supply. Anything that could be fixed on my end is better than shipping it back!

Anyway, sorry for an incredibly long post. I'd really appreciate some advice from people that are more experienced than me with this kind of thing.

Just as an update, I changed drivers back to the Nforce 4 Intel SLI Edition that I was using before. While I was swapping drivers there was a shutdown. Now the power button on my power supply doesn't work; I can still shutdown from XP, but nothing when I use the switch. It's stuck in "on".

I guess this narrows it to system or board? I have a 480 watt power supply that I could use to spot check, just not sure if it's enough juice to use with this PCI-Express system.

I would do this.

Let windows find all the drivers and updates from the CD rom and the windows up date site.
Ensure your BIOS is the latest version
run memtest again on the new ram
(I would have bought 2 512s instead of 1gb for duel channel purposes - but what you have is ok)
If you still have memory problems, remove everything except the video, ram, floppy drive (with memtest 86+ on it) and reboot and check.
If you're still getting errors after that, you have a motherboard power or bad ram. IT is unlikely to have two new batches of RAM be bad (not unheard of though)
I don't recall what your video card was, but some of the newer ones require a lot of juice.

I did check the new memory with Memtest... should have mentioned that. Two ten hour tests to make sure. Also XP and the bios have been updated.

Unfortunately I can't duplicate the problem I'm having now: random shutdown and the power switch on the power supply doesn't work.

Basically, it was like this:

I had memory problems AND BSODs. I replaced the bad memory, everything but the BSODs went away. Mobo drivers at this point were Nforce4 SLI Edition drivers.

Changed to Nforce4 AMD/Intel x16 drivers - now random shutdowns.

Changed back to Nforce4 SLI Edition drivers (last night) - power supply switch broke, no shutdowns yet but it's only been 12 hours.

So it's definitely two problems. The initial bad memory stick, and whatever is causing the switch problem / shutdowns.

Can a faulty motherboard cause a power supply switch to just not work, or is that definitely the supply? I would love it to be the supply because that's easily fixed.

Thanks much for the input.

dammit my problem is real similar to urs, except my system is only 1 month old!!! u know how much dat sucks, freaking bad_pool_header BSODS, ruining my life, anyone help me as well?

If the power switch on the PSU does not work, there is a good chance it has been arcing and possibly causing damage. Replace the PSU before it does any more damage to your PC's components, and don't use the switch again.