memory sticks

Can someone tell me the correct 184 pin memory sticks for DELL dimension 8100, optiplex gx400, and other mobo's of that vintage. As an example I am using 800-40, 800-45, c00-53, of mixed brands and capacities in pairs using slots 1 and 2 then 3 and 4 counting from the cpu to the psu in that order. I found that not all brands use the 800-40 notation, I have know way of knowing if these sticks are compatible. All I can tell you is that my collection of sticks all came from those models or similar. On another note, I have a 8100 that I converted to a 400 using that board. I had a hard time in reloading the XP OS using that tower. I ended up transplanting the hdd into my primary tower, loading XP, re transplanting it and then attempting to reload browsers, programs. I got as far as #7, and then installer errors from then on regardless of program, source, or browser. Then the dreaded BLUE SCREEN. More times than I can count. At this point the system is spread out on my kitchen table, connected as a system. The on board white led DOES work, but there NO GREEN lights on the power board, nor does the fan work. I am stymied. There are lit diagnostic lites but I have no way of knowing what they mean. I have a complete system coming in the form of extra parts, board, psu, ect. Is it possible that the PSU can be PARTIALLY bad? The mobo being also partially or fully bad? Any and all help welcome. Until I reassemble the system I have no idea of what the issue is. Thanks.