A lot of older computers, around when the P3's were popular, opened after you moved two little clip-looking thingies upward and yanked off the left side-panel of the case. You might try that. When in doubt, unscrew everything and pull. carefully. lol. But yea it def sounds like a burnt psu. does the little green (or orange) light come on when its plugged in?
Intel Conroe e6750
SLI EVGA 8800gts KO's
4GB Patriot DDR2 800mhz
22" Widescreen Sceptre LCD monitor 5ms
OCZ 700W psu
320gb seagate w/ perpindicular tech.
Creative SB X-Fi Fatality
Thermaltake Armor: Extreme Edition