Google it dude..
This is what I got:
Neither 2000 nor XP can be booted into DOS as a bootup option, at least not without using startup disks. In both cases they have an msdos.sys file in the root of c:\, but they're just blank files. You can choose "safe mode - command prompt" when starting up using the F8 key, but you'll still have to log in for security reasons.... and all it is is a dos emulator.