New Power Supply? you may want a new case!
You really have the stuff packed in there don't you. Anyway, consider getting an 80gb drive. Price per gig, you usually can't beat it (by much anyway). Best Buy and Circuit City have them on sale all the time.
And yes, I agree with you getting rid of the zip. Spend a day copying all of your zip disk files to CD-R's (if you have any), and unhook the zip drive. However, leave it in the case... just in case (that sounds funny) you need to read a zip. this way, it's just a cable move to access it.