Help with Minidumps from BSOD - XP Home, sp3

My XP Home SP3 continues to get random BSOD's, it will be ok for hours and/or 30 minutes and poof. The Error codes I get are headed by 0x00000050. Next set of 4 - 0x numbers stays the same for the last 3 sets, the 1st changes. Last 4 examples are:
0X00000050
(0x8B91B000, 0x00000001, 0x80541678, 0x00000000) and
(0xB43EB000, 0x00000001, 0x80541678, 0x00000000) and
(0xB287B000, 0x00000001, 0x80541678, 0x00000000) and
(0xB3316000, 0x00000001, 0x80541678, 0x00000000)

Two (2) of the associated mini dumps are at:

https://skydrive.live.com/#cid=786A5682C795A834&id=786A5682C795A834!105

The 1st and last were simply not there. I have no idea why not.

I have XP Professional 64 bit on a separate hard drive. It has been running without error with all the non 64 bit drivers the same.

Have 4, 1gig sticks of RAM, ran extended Memtest on all 4 without any errors. Did them all singly, then as pairs, then as a total set.

GPA Student tried to help, that thread can be found at:
http://www.GeekPolice.net/t28498-bsod-help#196407

Hoping that starting a new thread will help.

Searching microsoft suppost for 0x50 errors has lead to fixes for Backdoor virus/worm, memory issues, etc, etc - none of which help.

Thanks

Hi, me again, I know your RAM passed memtest. I don't trust memtest 100%. I think I suggested pulling a memory stick or two and run that way for a while.