BSOD 4GB, 2GB fine

Soooo, similar to another thread of similar name I'm having a similar problem.

I will start with story:
XPSP3 installed for roughly 12 months. Then about 2 months ago, started to have small problems with the C: disk. Random crashes of programs, stuff like that. About 7 weeks ago, then had actual disk errors, "windows can't write to disk" blah blah. Was fine again for a week, then it had major more problems. I turned off the ACPI error thingy, (can't remember on new install have logs on there but can't access), and that let me boot again (previously dropped back to UDMA1 or 2, so was like 1MB/s) and use it.

Then about 4 weeks ago, started getting even worse, so started preparing for new HDD and such.

Week or so ago, bought hardware for server (2x2TB) and started moving everything off the dodgy drive onto another, then onto the server (still plugged in, internal > Gbit ).

Then, barely 36 hours ago, it totally spit the mickey and wasn't able to get in, so had to use a backup I had put on 3rd disk about a week before. It had major similar problems as well (possibly cos original HDD had corrupt, so the backup image also had corrupt stuff), but I limped along then installed W7 after work. Barely 30 minutes after seeing the desktop, BSOD! It complained about memory_management and as such I took out B slot 2GB. Was fine for while, played COD5 no problem, then I put stick back in rebooted after updating, and BAM, another BSOD. Tried install Adobe, it was corrupt and BSOD after 3rd try to DL. Then did mem test for 2 hours, with both sticks in, no problems.

Came back, played COD5WAW for about 4 hours with both sticks in, no problem. Close down and start watching simpsons, check email, BAM another BSOD. Take out 1st stick this time, and as such have been stable for about 4 hours now.

1. Haven't updated bios, but NO changes to hardware at all in 12 months.
2. Ran seatools on the HDD, didn't find any problem even with long test.
3. Memtest run on both modules at once, no problems

Now, I don't have a clue where the actual problem is, there are so many different things breaking. First the HDD errors on XP, then the BSOD, now similar on this W7 install. The only part that makes much sense is the motherboard being slightly damaged or something, or the RAM slots whereby 2 causes slightly to much voltage leak or something.

Anyway, have attached minidump of most recent crash. Any help would be great, though come Monday I'll try convince boss to salary sacrifice an Asus G73JH-TZ008X for me

Oh, specs:
Asis M4A79 Deluxe
Corsair DDR2 4GB PC-8500/1066 (2x XMS2 2GB) TWIN2X4096-8500C5D
Asus 4890 1GB
PII 955 BE
Corsair 620HX
Bunch of 1/1.5TB Seagates, some crappy DVD burner and that is about it.

Oh one thing I remember, when booting up it says 800Mhz Unganged mode.

I remember researching that when I got it 12 months ago, but can't remember what I found. I'm curious now actually why it is only running at 800Mhz vs the 1066Mhz, anyone know that either?

Well, your mobo manual specifically states:
4 x DIMM, Max. 16 GB, DDR2 1300(O.C.)/1200(O.C.)/1066*/800/667 ECC,Non-ECC,Un-buffered Memory
Dual Channel memory architecture
*Due to AMD CPU limitation, DDR2 1066 is supported by AM2+ / AM3 CPU for one DIMM per channel only. Refer to ASUSTeK Computer for the memory QVL (Qualified Vendors Lists).
**Due to OS limitation, when installing total memory of 4GB capacity or more, Windows® 32-bit operation system may only recognize less than 3GB. Hence, a total installed memory of less than 3GB is recommended.

Note the ** warning.............. 1 DIMM per channel

Hmmmm, but I hadn't changed anything in almost 12 months. Surely it wouldn't have worked for that long and then not?

Anyway, just looked at the RAM slots, and the 1st stick, currently running on, is in DIMM A1, and the 2nd one was in DIMM B1. IE, both the yellow slots.

That is how the mobo says it should be done for 1 DIMM per channel, but now that I think about it, it says if you run 4, and it doesn't like it, it will drop the speed to 800Mhz, which might explain why it says that.

I'll try sticking the 2nd into DIMM A2 (ie, next to 1st, in the black slot), and see how it goes.

Might also perform a CMOS reset/update but again, if it worked all this time.. :S

Hmm, seems to boot still. It still says 800Mhz unganged, didn't see any difference.

W7 reports 4GB as well.

I'll do some hardcore stuff and see if it dies.