you can set a disk letter with the administrative tool like archd already said. if windows' "forgets" the letter of an external hard disk and there is no way to prevent that feel free to post a feature request at microsoft developers network, because that's quite a basic feature that can be implemented without breaking stuff ontop of it (so it could be distributed with the windows update service).
Quote: Originally Posted by
FlamingShade 
i think the letters are assigned according to the order u insert the disks so whichever disk u need F, insert it before the one u want as G.
at least that's what i think
nope. windows doesnot remember the order in which hard disks were connected. the order of windows partitions autolabeling is c:\ for the windows' installed disks' primary partition, d:\ for the secondary partition of the windows-containg disk, ...
then come all partitions of the other disks in hardware detection order ( see bios autodetecting ), again starting with primary and going on with extended / logical / whatever partitions.

2009-01 uploads:
☆akasaka
☆haruka naru toki no naka de - hachiyoushou
☆haruka naru toki no naka de - kurenai no tsuki
☆haruka naru toki no naka de - maihito yo
☆telepathy shoujo ran
★all of marimite that gets released by chihiro
★all of zoku natsume yuujinchou that gets released by bss
☆akichan once the last two episodes get subbed