Help - RAM Diagnostic Tool and General Win7 Problems

I wasn't sure whether to put this in the hardware forum so forgive me and please move if appropriate!

I purchased 4GB of RAm a few mnths ago and also got a copy of Vista HP64. From the get go I had all sort of issues in Vista - games would not run, the OS seemed to crash a lot, would get messages like MS Outlooks data file was not closed properly. Windows defender would crash all the time.Tried about 15 different nVidia drivers... gave up. I tried 3 different HDDs too.

So anyway I moved back to XP because I assumed it was simply Vista.

This week I downloaded Win7RC1!! I'd heard nothing but greta things on podcasts, in forums etc. So i installed.

From the start I've had again defender crashing, "windows logon" errors, action centre shows me a LOT of errors that it's detetced and fixed. I get a few "explorer has stopped working" errors too. UGH! Games do not work - they freeze either on loading or after 30 seconds or so of gaming. I've had 4 or so BSODs which I had heard were basically unheard of in Win7! They were of varying variety.

All these erros in 3 days worth of running Win7? Seems a lot.... and errors on core components of Win7 too.

http://img90.imageshack.us/img90/9194/crashes1.png

http://img89.imageshack.us/img89/8281/crashes2.png

I ran Memtest86 and both my 2gb modules passsed multiple runs. I figured the RAM was ok. I swapped in a different graphics card, still the same problems. I went to the drastic measures of buying a new MB - figured it was worth a shot. Still no improvements.

So I ran Windows Memorty Diagnotisc and it returned a pass on Standard mode, but returned errors on extended mode. Took out one of the modules. Passed on extended mode. Put the other module in - failed on extended mode.

It fails at 21% on extended mode... well it tells me it detected a hardware error. Is Windows diagnostic more thorough than memtest86? Why does the windows tool pickup errors but not in something as well trusted as memtest86?

So given one module fails extended test and one passes, do you think that my RAM has been the source of all these issues Ive descibed both in Vista and Win7? In XP I didn;t seem to have too many problems.... but perhaps because I was only addressing ~3gb of RAM not the full 4gb?

I'm teraing my hair out on possible solutions :/ Any advice? Do you think my RAM is faulty if it comes up with an error in the windows tool on extended mode?

Anyone other memory testing tools I can try to get a confirmation the RAM is faulty?

------------

The annoying thing is, no results of the windows tool are displayed other than this I found going though the Action Center. Annoyingly it leaves out all the details of the error. This is on the one stick of RAM that gets an error on extended mode:

Description
The results of running the Windows Memory Diagnostic were submitted to Microsoft for analysis and product improvement

Problem signature
Problem Event Name: MemDiagV1
Range of memory size: 0
Launch type: Manual
Schedule type: Immediate
Completion type: MemTestError
Test type: Unknown
Failed tests: 0
Number of bad pages: 0
Test duration in seconds: 0
OS Version: 6.1.7100.2.0.0.256.1
Locale ID: 3081

And this is the other "good stick" which actually shows the details. Very strange:

Description
The results of running the Windows Memory Diagnostic were submitted to Microsoft for analysis and product improvement

Problem signature
Problem Event Name: MemDiagV1
Range of memory size: 2048
Launch type: Manual
Schedule type: Immediate
Completion type: Pass
Test type: Custom
Failed tests: 0
Number of bad pages: 0
Test duration in seconds: 1170
OS Version: 6.1.7100.2.0.0.256.1
Locale ID: 3081

Files that help describe the problem
MemDiag.bin

Try running with just the good module inserted. That'll (most likely) tell you if it's the RAM or not.

Memory tests are software assessments of the bits being sent through the RAM - so there's lot's of other things that can cause errors. If you're curious, read the documentation that comes with MemTest.