[Fractint] OT - Need a DOS prompt!

My apologies in advance for an OT post. Fellow Fractint Fanatics: My fractal explorations are on hold right now, as my PC refuses to boot because of a file my son downloaded. I can't even get to safe mode. I have figured out what to do to fix the machine, but I need to get to a DOS prompt, and I can't seem to do it. I made a rescue floppy with Dr DOS on it, but each time I try to exit to DOS I just get another re-boot. Can anyone pass advice as to how to get to a DOS prompt? Maybe a DOS only disk I could boot with? I have used PCs since before Windows existed, but the lack of what used to be basic tools (like floppies to boot from) has got me stymied. Marty K