You don't need an old version of Dos. Simply format a floppy disk but with the box 'Copy system files' ticked.
Easier than that - go and edit the file C:\MSDOS.SYS and add the following lines in the [options] section:
Code:
BootKeys=1
BootMenu=1
BootMenuDefault=1
BootMenuDelay=5
Then, every time you boot the computer you will be presented with a menu. For the bare minimum select 'safe command prompt'.