you will DEFINATELY need a new power supply, 90 watts is nothin, you need at leat 235, 260+ would be even better...
as for a case, you have a gateway, you'll probably need a new case too....most are proprietary
i dont think you'd need a new sound card unless you want a new one
as for ram, if you use SDRam (DIMMS) it will work fine in a new box if you go with a celeron/intel system. it will not work with an AMD system, as all the new AMD systems use DDR ram.
theres some good deals there on barebones systems, i might be able to do better...decide how fast you want to go, and make a list of exactly what you have in your old computer (part names and such, available from the device manager) and ill see what i can put together for ya
