7GB is very little for three OSs (to my concern at least)
you may want to check this thread
and slightly adapt it to suit your needs.
I can't tell you which device is for "drive E"
drive letters are arbitrary "adresses" given by windows to all supported partitions found (that is FAT, FAT32 and NTFS), you may even change them if you don't like it the way windows does it automatically.
what you want to know is what number the partition has on your hd, and eventually the disk label (make sure you set it to something usefull, like "WINXP", "WIN98" and so on, to prevent yourself from doing something stupid when playing around with the partition table.
when installing grub on the bootloader (check the linked thread above), you should be able to have one entry fro linux, one for win98, and one for winxp.
ps: install win98 first, then XP, then linux, and try to see which partition windows uses to boot so you can point your grub to the right place.
pps: you may have to myke a generic grub entry for "All Windows" and then you'll get the windows bootloader (ugly black and white) to chose between win98 and winXP