You may find yourself in trouble when you boot from a disk which includes CD ROM drivers and then try to reboot after running the installation procedure. Ramdrive.sys, which comes with Windows, is unsuitable because you cannot assign a drive letter. Because the system will later run from CD and the CD ROM drive can only be assigned a drive letter which hasn't been assigned yet, the system should be installed on a drive with a letter from the back of the alphabet. This is important to make all registry links and paths partition-independent. Instead of setting up a number of dummy partitions, you can use the subst DOS command to assign a drive letter to a hard disk directory of your choice.
Similar things apply to files called system.dat.
However, to get to them you must leave Windows and reboot the computer to its command line. This may cause the wrong system.dat to be booted and might even influence other installations. Setup will complain that subst.exe is loaded. Ignore this message by pressing ESC against the program's recommendation. The first installation reboot must be done from the Windows startup floppy you made previously.