120GB is pretty big for Win98 let alone dos!
I agree if its just for gaming you typically don't really need an old version of dos as well as the copy that sits under Win98. You can then select restart in dos mode from within windows for a clean dos environment AND have a fully working Win98 PC.
My partition map usually looks like this assuming its just Win98 installed
C:\ 2GB, Primary partition , Win98, Fat32 (I really don't trust OS been installed on large partitions)
Assign rest of the drive as extended in fdisk.
D:\ No set size, logical drive, Fat32, "Games drives" this is where I install all my games and misc files
E:\ No set size, logical drive, Fat32 "recovery drive" Drivers, Windows cab files,
"Dos 7" can read all this and as a bonus if I ever need to reinstall windows I don't need to reinstall alot of the games (dos ones won't even know the difference)
Also tools like scandisk dont take so long to complete. I ran defrag on a 80GB drive last week, that took over 24hrs!