- Disabling floppy drive in bios (This didn't help, but I'm sure it will speed things up slightly as I don't have a floppy drive)
- Set the "IDE detect time out (sec)" to 0. It was originally 35. (This didn't help. Be careful when changing this option if you are using IDE drives)
- Unplugged the SATA cable from my DVD drive and plugged it back in again. (PROBLEM SOLVED!)
I imagine either my sata cable is slightly loose or dodgy and reseating it has sorted the problem. If the problem occurs again then I will replace the cable.