As part of my (slow) migration I have the following disks/ partitions...

hda: Linux (only)
hdb: cdrom
hdc1: w2k
hdc2: w98 (see below)
hdd: w98

hdc2 is a copy of hdd using file explorer from w2k (this seemed the safest way to do it). GRUB is already set up to offer booting from hda, hdc1 and hdd. What I now want to do is to boot w98 from hdc2 instead of hdd (so I free up hdd completely). I realise that hdc2 is now missing the mbr for win98 but what can I do (preferably without losing w2k)? Reinstalling win98 is not a practical option.

The GRUB syntax is simple (once you get the hang of it)

Include for windows:

title: windows 98
(hd2,1) chainloader+1 rootnoverify

and that should do it.

(GRUB counts hdds and partitions starting from 0 -> hda=hd0; hdb2=hd1,1)

Thanks linmix but atm my GRUB entry for the migrated partition is...

title w98-2
map (hd1) (hd0)
map (hd0) (hd1)
rootnoverify (hd1,1)
makeactive
chainloader +1

...and using (hd2,1) would point to the original drive. Further to posting I'm wondering if I could get away with dd'ing the boot sector from the original drive to the new partition without screwing things up. Anyone got any thoughts on this?

in grub hda=hd0, hdb=hd1, hdc=hd2 and hdd=hd3

I don't know about the map entry though. Never used it.