Question : Problem: is it absolutely necessary to get a new power suppy if...

im upgrading processor and ram in a 6 year old dell dimension 4500
current specs:
dell dim 4500
windows xp service pack 2 home edition (build 2600)
motherboard intel D845EPT2   i845e chipset
nvidia agp gforce mx 420
internal drive: 40 g
external drive: 150 g
ram 512
 ----i want to add: 1) intel pentium 4 2.8 533mhz   2)double up on ram  3) and possibly a graphics card upgrade, maybe in the 60-120 dollar range

i have a basic heat sink and 250 watt factory power suppy/fan ----is it necessary to upgrade this stuff also???

Answer : Problem: is it absolutely necessary to get a new power suppy if...

Dalton --> Here's the Dell documentation on the 4500 pinout:
http://support.dell.com/support/edocs/systems/dim4500/techov.htm#1101836

... which matches an the standard ATX pinout (e.g. http://pinouts.ru/Power/atxpower_pinout.shtml )

... first thing I always do for a Dell PSU question is check the docs to see if it's one of the non-standard Dells ==> it sure looks like this is not.

I agree a large PSU would be nice ... but I don't think it's necessary UNLESS a more power-hungry video card is added.