I have a RH 7500 But dont start no more any help would be good?

Hi i have a RH 7500 which have worked well for a few years now but the other day i put it on and didnt work what happens is...
when i turn it on and i get scrolling HELLO on the screen and then it boots up to find channel it just reset it self and goes back to start the bit with the scrolling HELLO. Also the dvd tray wont open not sure if this is normal because it dont get to the full boot up i do know that the 80gb Hard drive is close to beening full not sure if this is a cause of it failing to boot up fully.
ALSO i was thinking if i took hard drive out and pluged into pc and reformated the hard drive would it sort out problem ?
Can the hard drive be taken out and put on pc is the other thing..
Well any help on the matter i would be greatfull as i dont realy want to have to go out and buy a new one at the moment.

Thanks