I blew it - bought a Dell Inspiron 530S at Staples a few years back. We have had nothing but problems! If we leave it on at night - it locks up at night, fan going full speed. We have to UNPLUG the stupid thing in the morning and then restart to get it going again. this has been going on since a few months after purchase...
Any suggestions besides taking the ol' sledgehammer to it?
With some computers going into stand by mode will cause this when using USB keyboards and a USB mouse. Some motherboards have jumpers by the USB ports to enable standby power to the ports if the USB's aren't getting power it will lock the computer up just like you say. Try going into device manager and go to your Keyboard and mouse properties and in the Power Management tab un check allow this device to wake computer. After you do this you will only be able to wake the computer by the power button this usually fixes that problem if it is even this.
You could just go into power management in control panel and tell it not to go into stand by mode.