System Failures - Memory Failure

XPS 400/Dimension 9150 Dual Core system 4G RAM upgrade.  XP Home o/s upgraded to XP Pro.

System shuts down sporatically, no warning, no memory dumps.  Enters a loop on restart where it starts to boot and then shuts off.  Ran Dell Diagonstics.  All heat related issues pass, i.e. fans, etc.

Memory issues fail as follows:

Error Core: 5800:042A Msg: CPU 0 Data error at address1622c10, expected 9d897033 but found 9d89703b

MATS test: Error code 2F00:OB1C msg: Memory data, data bus stress test failure

MARCH A test: Error code: 2F2F:0719 msg System Memory failure.  read FFFFFFF7H, expected FFFFFFFFh at address 00B93610, 00197610h, 00BA3610h, (plus many more).  Suspected memory component located on system board at Label DIMM_1

MARCH C test:  Multiple failures as in test A above.

 

After 1st tests pulled 2G RAM stick from DIMM_1.  Replaced with the other 2G stick from DIMM_3 and left DIMM_3 empty.  Ran tests again - same or very similar failures (i.e. some address locations were different).  Before I go buy SRAM as replacement would like opinions on whether or not this may be a motherboard problem.  And if so how might I test it to confirm that? Thanks.