Dell 8400 Checkpoint [Ithr]

I went away on holiday for a week and came back, started up the computer all working fine and go away for 10 mins and then it crashed. I turned it off and on several times getting nothing then i got a black screen with a message of this sort: Alert! Previous attempts at booting this computer have failed at Checkpoint [Ithr], contact customer services... i am rather puzzled by this as it has been fine for a while, can anyone please help me solve the problem?

 

Thanks

 

Adam