Noob question: Solving crash problems

[Skywatch]

First thing to do is to remove the overclocking and see if that helps.

Check the 5V psu and tell us its current rating. It may not be enough for the USB HDD as well (is the HDD powered with its own supply?)

Try adding a powered USB hub and connect that to the pi and all the usb devices to the hub.

It really sounds like it might be a power issue, but you could run a test on the SD card as well in case there are any errors on it.

Skywatch