is this my power supply

[Rx_cigerette]

so recently whenever i shut my computer off and try to turn it back on it takes a few trys to get the monitors keyboard and mouse to start up to. basically what happens is ill turn on my computer both activity lights are on can hear my hd's running, but my monitor keyboard and mouse stay off. what could be the cause of this it started recently and i haven't changed anything but i have heard my power supply isn't the greatest. I am kinda of hoping it is the power supply, just because i have been looking to replace it anyway this just gives me an excuse.
any ideas?

power supply: rosewill 500w (rd500-2db)
http://www.newegg.com/Product/Product.aspx?Item=N82E16817182044&Tpk=rd500-2db
Motherboard:ASUS m3n-ht deluxe
http://www.newegg.com/Product/Product.aspx?Item=N82E16813131343
Memory: ocz vista upgrade ram 4gb ddr2 800
CPU: amd athlon 64x2 5200+
Gpu: evga 9600 gso
HDD: seagate barracuda 320gb
HDD: maxtor 250 gb
if you need any other info please tell me.

 

[Dangman]

Short Answer: PSU

Long Answer: Could be a mobo, shorting, PSU or maybe a combination of all three.

 

[engiNURD]

... or the ram not playing nice with your board.