Occasional Kernel 41 crashes but always in memory disgnostic

I've been running Win 7 Ultimate Retail happily for over a year on this PC.

I started getting occasional crashes a few weeks ago, no BSOD just a complete and sudden restart. It started getting more and more frequent until it always crashed during startup.

BUT, it worked fine in safe mode - no crashes even after running for days.

I tried removing various drivers etc. to no avail so I decided to give up and do a clean install.

While doing this I decided I might as well upgrade the 256gb HD to a 1Tb drive which I did.

All went well but checking the system out after the install I found that it crashed during Windows Memory Diagnostic. It's fine with Memtest86.

I dug around the web and found references to a graphic error (it's on the mobo) so I put in a HD5450 (I now have a DVI connection to the monitor) and changed the BIOS etc.

Still the crash in Memdiag, and one apparently random crash too. More digging and I see that the original power supply at 305W is a bit weak so I've put in a GX 550W supply.

Still the crash in Memdiag and another in the middle of the night while it was just switched on with no programs running.

The event viewer
shows

-System
-Provider[ Name] Microsoft-Windows-Kernel-Power[ Guid] {331C3B3A-2005-44C2-AC5E-77220C37D6B4}
EventID41Version2Level1Task63Opcode0Keywords0x8000000000000002-TimeCreated[ SystemTime] 2011-09-28T00:09:06.869223500Z
EventRecordID9328Correlation-Execution[ ProcessID] 4[ ThreadID] 8
ChannelSystemComputerGM_DELL_APR06-Security[ UserID] S-1-5-18

-EventData
BugcheckCode0BugcheckParameter10x0BugcheckParameter20x0BugcheckParameter30x0BugcheckParameter40x0SleepInProgressfalsePowerButtonTimestamp0

It's a Dell Dimension 5150 2.8GHz with 3Gb memory.

I'll be grateful for any ideas. TIA.

Thanks, I've done that. I was only offered a 128kb dump so I chose that.

I generated a crash by running by running memory diagnostic again.

Looking at the files I don't have any kernel dump files, just the following.


28/09/2011 11:52:12.04
28/09/2011 11:52:12.04


LISTING OF MINI KERNEL DUMP FILES
LISTING OF MINI KERNEL DUMP FILES





_______________________________________________________

28/09/2011 11:52:12.10
28/09/2011 11:52:12.10


FULL KERNEL DUMP FILE
FULL KERNEL DUMP FILE


Volume in drive C has no label.
Volume Serial Number is 068C-EDC9
Directory of C:\Windows


I noticed when running the exe that the first message is a 'path not found'.

I seem to have had an occasional (1 or 2) crash in the upper memory part of test 8 while other runs are OK.

I have 3gb made up of 2 x 1gb and 2 x 512gb (the original memory).

I ran Memtest86+ on each of the 1gb in slot 1 over the weekend. 36 hours and 24 hours. No errors.

I put both in again, slot 1 and slot 2 and ran the test for 2 passes this morning. No errors.

I then tried Windows Memory Diagnostic again twice. Both times it crashed at 15%.

I noticed that after the memdiag crashes, although the keyboard was working it seemed as if the mouse had to reinstall again (USB port?) and didn't respond for over 10 minutes.

I've now run Memtest86+ for 15 hours against the two 1Gb sticks with no errors but it still crashes at 15% in Windows Memory Diagnostic.

Any ideas please?

Interestingly if I run Windows Memory Diagnostic against either 1Gb in Slot A it completes OK.

Is this possibly a Slot B problem?

Still plugging away at this.

I put another 2 x 1Gb in slots 3 and 4 and now memtest86+ crashes out soon after starting and there are random crashes while the machine is running.

Is this a memory, slot or CPU problem?