Power supply not turning on

I built an HTPC using an Asus P5W DH motherboard, recomended Corsair memory, OCZ 700 watt PS, Auzentech sound ect. verry Low hours for about a year. My problem is< it wont power up now. Checked CoolerMaster case swicth, its was ok, jump started PS per OCZ instructions, and it powers up, all externals are unpluged. Any sugestions? I was going to start unpluging cards next. I paid a lot for this MB a year ago, and found everone that had it was having troble, getting the hard drives set up, ect. If a MB replacement is needed, can someone recomend a good replacement. I also have an Nvida dual tuner card in it , and a 8500GT vidio card, and outboard HDHome run, I was just setting up. Thank You.

Despite "jumpstarting", unless the psu then powered your system, the first thing I'd suspect is the psu.

Unless you recently opened the case and did something . . .