Hi, I'm having some problems with a PC I just built and was wondering if anyone could help. Everything seemed to be working fine, I had installed Windows 7 and was downloading Team Fortress 2 from Steam when I left the computer to go and cook myself a meal. I can't have been gone more than an hour or so but when I came back the computer had frozen and stopped displaying output to the monitor so I shut it down using the power button. Now when I try to power up the PC the blue power light on the case comes on as do the chassis fans in my case, however no output is displayed to my monitor via either my graphics card or the Intel integrated graphics on the motherboard. Also USB devices such as my mouse and keyboard don't seem to be receiving any power from the built in USB ports on the motherboard or the USB ports built into my case (the light in my optical mouse doesn't light up when I try turning on the computer). The hardware in my computer is as follows: Asus P8Z68-V LE Motherboard Intel Core i5-2500k Processor (2nd Generation Corsair Cooling Air Series A50 Performance CPU Cooler 4GB Mushkin Blackline(2x2GB) DDR3 1600MHz 9-9-9-24 RAM 500GB Western Digital Caviar Black HDD EVGA GeForce GTX 550Ti 1024MB PCIE Graphics Card 800W Mushkin Enhanced Joule ATX 2.3 Power Supply LG 22x DVD-RW Drive If anyone can offer any help or advice I'd be very grateful, also please let me know if you need any more information. Thanks.