+1 if you have a Dell then it is pretty much an exercise in futility to try to replace parts with non Dell stuff (except easy stuff like RAM).
It would be better/easier to either:
1) Get a new computer, copy data from old one (data meaning pictures, videos, documents, etc, not the OS)
2) Get a new case, power supply, motherboard, CPU, RAM, and move over the hard drive from the Dell, may still have to reinstall Windoh's, but it may work
3) Get a Mac and be done
4) Get Linux and be cool! :supergrin:
For an anecdote, I have a custom built PC that I just recently upgraded from an AMD64 (first gen, socket 754) to an AMD64x2 (socket AM2+), with new motherboard, RAM, videocard, and SATA DVD. Kept the hard drives, did not have to reinstall Windows (or Linux). However I kept with the same brand mobo (Gigabyte), though different chipset (old = Via, new = AMD), and kept with same architecture (AMD64). I run Windoh's XP and Fedora Linux, neither had any real hiccups when doing the switch over.
If you want to stick with brand name prebuilt computers it is easier to stick with them and only upgrade small bits (RAM, new video card maybe, hard drive), and get a new brand name system when it is time to upgrade. If you want to do your own major upgrades it is better to stick with custom built.
Just fyi, in my case-
Upgraded:
Motherboard (both Gigabyte)
CPU (AMD64 to AMD64x2)
RAM (DDR PC2700 to DDR2 PC8400)
Video (GeForce 6600GT to 8800GT)
DVDRW (IDE to SATA)
Kept:
Case (Coolermaster aluminum)
Powersupply (400W I think it is, Thermaltake)
CPU cooler (monster Thermaltake, works with AMD socket 754 and up to current AM2)
Hard drives (1 for Windohs, 1 for Linux, 1 for random data)
Soundcard (SB Live, works well with Linux, yes new mobo has built in, but eh)