Can't reset 7n400pro

bought a 7n400 pro and can't get the thing to reset (switch or reset) I have twice had the cold boot problem mentioned elsewhere but mostly touching the reset switch or when windows install tries to soft reset during install I just get a black screen and no post or anything!?? Arrrghhhh
Haven't seen this anywhere else on any boards - could it be my cheap ATX PSU?

7n400 pro
1800xp
gf 5200 agp 8x
1gb ram (dimm 1&3)