Computer won't boot in safe mode with command prompt?

My computer crashed and I am unable to get it to boot up and run (using an alternate laptop, MAC, sadly). I've tried booting from a CD and even a USB flash drive, but the screen just goes to black. When I can at least get it to try and run in Safe Mode with command prompt I see that it halts after isapnp.sys and it will just sit there until the computer is shut off again. Is there a way to enter DOS mode or to correct this issue with whatever is going on with isapnp.sys or what is coming right after it?