I hate trying to fix some of that old dell stuff. Some of it is ok, but i don't like it when they make a special power supply connector that is only made by them. Some of the older Dells tried the ole BTX form factor, which is a pain to upgrade some stuff, and RD ram which is wierd too. But they have been getting away from some of that. They don't make much anymore, PSUs, some motherboards and cases....but it seems like they are getting away from motherboards and ram etc...
I was gonna upgrade a XPS400 one time, and quickly squashed that idea. lol. Seemed easier to start from scratch. I recently worked on a couple year old Alienware (bought by dell) and it had XFX motherboard and corsair ram....nothing dell...lol. They couldnt figure out the BSOD the guy was getting. Replaced his mobo, ram, psu, and vid card. lmao. It still blue screened. I switched my corsair ram with his (different model, timings) and no more BSOD. I thought that was funny. He got some free new stuff anyway.