Help HTC Desire S - Only Shows HTC logo

[Tsail186045]

I recently bought a HTC Desire S secondhand, however when it arrived I turned it on to find that it just displays the HTC logo then a black screen. It has 4ext installed - which is what loads when try to do a factory reset.

I have no experience with installing custom ROMs but I'm pretty good at following instructions. I'm hoping that someone here will be able to tell me how to fix this!

EDIT:
Some more information, the boot loader menu says:
*** UNLOCKED ***
Saga PVT SHIP S-ON RL
HBOOT-2.00.002
RADIO-3822.10.08.04_M
eMMC-boot

Thank you for any help,
Tom