best solution for this in my opinion:
1. keep the WD 80gb SE and put it in a new system if thats what your doing.
2. if you can, get a p4 chip, cause the fans on the p4's are bigger and A LOT quieter than those on AMD chips [because theyre bigger, they spin at lower rpms = quieter]. if you have an AMD chip right now, i can almost guarantee that the cpu fan is making the most noise of anything.
3. buy that sound dampening material that ibooken@mwny linked to. its really cheap and will probably help a bunch. [im buying some for my PC as soon as i get the chance]
4. also, if you get a p4 you really only need 1 80mm case fan, most likely mounted in the back, pulling air out of the case. p4's dont get as hot as AMD's, and you dont need the extra fan pulling air in from the front. [this also pulls in extra dust and makes extra noise].
5. p4s are also competitively priced now, so... yeah get a p4
some other stuff: i have 3 hardrives in my pc: 2 15gb maxtors and a WD 80gbSE [same as yours, computer_phreak], and those 3 drives combined with all the other fans in the case STILL dont make as much noise as the cpu fan. i know cause ive manually/phisically halted the cpu fan for a couple seconds, just to observe how much noise it was actually making.
hope that helps.