My PC won't boot

My PC will not boot, when I turn it on it goes to the advent screen where you can press tab or del to enter setup then the screen goes black. At this point it usually waits a couple of seconds then gives me the choice of which OS to boot, 7 or XP, but the screen just stays black with a cursor flashing in top left corner.
Anybody got any ideas on what to do?
Ive entered setup and looked through the options and everything looks normal, all the RAM and HDD's are detected etc but I admit I don't really know what im looking at.

 

Try changing the boot order?

Do you have a disc in the drive or stuff plugged into USB?

 

I unplugged everything from the USB ports and it works. Thing is, there's nothing new in there, just the same stuff ive had in all the time. External HDD, External DVDRW, printer, mouse, gamepad, micro usb phone lead and dongle. I don't get it.
Ah well, as long as its on I can virus check and stuff.

 

How do I check the boot order?

 

Try holding F8 on system startup, that's how I bring up my boot order.

 

Herp Derp a dooderp, my bad.

 

I think it's F2 for Setup. Then scroll over to the tab that clearly shows the different devices (HDD and DVD Drive) I would put the DVD drive first just in case your computer decides to erase its own boot sequence like mine did, unless you have Boot Menu (F8).

 

It comes at the start up screen. For my PC it is ESC and for my laptop it is F2.