I think you are mixing up booting, and switching to.
If windows is down, you cannot get to a dos prompt in anything since 98. (although you can use various universal recovery disks)
You really don’t know Windows. 1) You can boot to a command prompt in safe mode if the system goes into automatic recovery mode; 2) you can boot to c:\ from a boot disk or the installation disk; 3) you can set up boot options ahead of time to allow you to boot to c:\ any time you restart; 4) you can access a c:\ prompt in safe mode by logging on as another user; and 5) you can go to a command line from a system window. The last 2 require being in windows, but the first 3 can be done when you are cold booting or windows in not accessible.