How can I get to a terminal when Windows won't start?

[dane47]

My Dell desk top won't start Windows or go into Safe mode.I remember once on a windows computer years ago I used a terminal to get the computer to scan itself.How do I get to that terminal on Windows 7 and what should I type in?
I am getting the error of page-fault-in -nonpaged-area.This computer is only a year old but came with a very limited warrantee.
I want to go back to the original Vista as soon as I can. Before I got this error,I had to verify my version three times.What commands would I use to delete Windows 7?
This computer is only a year old and the newest of my computers.
It should be working.

 

[das_stig]

When windows starts to boot just after bios post, press F8 for options and one of them is startup with a command prompt.

After that, use chkdsk<space>/f to tell windows to schedule a scan on next boot.

Then simply restart windows.

Dell normally provide a recover partition by hitting one of the F keys or when you get into windows, a piece of software to do a recovery.