Stumped

Could anyone please help me with this frustrating problem ? The computer will not boot up and cannot get to safe mode! I have had the hard drives checked and they have been found to be ok ! What i was hoping to do was access the computer to DOS and format the whole drive ! Could anyone suggest alternatives for getting into safe mode ? This is the first time i have asked a question on a forum so i hope you can understand the problem i am having.

Thanks in anticipation

Geoffersau.