Undo faith in GRUB and RH7.3 means I can't access my XP partition. Please help.

[Mark Berkwitt]

I tried a dual boot install of RH7.3 after XP was installed first.
I've had good success with RH lately so I figured I could let grub write to
hda instead of hda3 '/'.
I tried using my xp cd to do a repair but I can't remember my Admin
password.
I can still boot into RH via grub or floppy so how can I either fix the mbr
(return to boot xp) or secondly tame grub to offer both os's at boot?
I do happen to have a win98 2ed, floppy, dos boot disk.
I'm afraid to just try something, but I could use one of the older os's to
do >fdisk /mbr. Is the syntax ok?