Replacing power supply ATX

[NETtek7]

I am working on a computer which currently works with my computers ATX power supply. It does not boot with its original power supply, which is an Antec model - ATX90-3405. The powerless computer, a HP Pavilion, has an ATX board(which is a redundant statement at the least). I am not sure as to what power supply I should replace it with. I am having difficulty finding one that could fit in the original case(and screw in properly). At the same time I am wondering if I should replace the case and powersupply all together. I will list the powersupply's specs and dimensions. Thanks for the help if any. http://www.PCGuide.com/ubb/biggrin.gif

INPUT 100-127 V ~ 3A
200 - 240V ~ 1.5A

OUTPUT +12V, 1.5A
MAX +5 V, 12A
+3.3V, 6A
-12V, 0.2A
+5V SB, .72A


TOTAL POWER ON +3.3V & 5V is 70W MAX

MAX CONTINUOUS OUTPUT POWER IS 90W

Thanks again.