Originally posted by Rogerio
my mobo is ECS Elitegroup P4M800-M7
That is your problem. Every mobo I've delt with from ECS is problematic. As in my sig, I had a KV2 Extreme a year ago...temp sensors were useless, one of the two ethernet ports didn't work, two of the four USB ports "caved", and the computer randomly reset when booting up (I think due to it thinking the voltages were low, even though this setting was off in the BIOS)... Bah, sorry to nag, I just hate ECS with a passion, now...
Nonetheless I would check your graphics card as well--and as they've said, ensure all cables are snug and plugged in... And your mobo wouldn't just fry from adding some USB stuff, unless you really went crazy...hehe...