When using mozilla firebird on W2K/XP, your profile is stored in
C:\Documents and Settings\<name of your profile>\Application Data\Phoenix\Profiles\
in this profiles dir there is probably a dir called default. enter this one, then there is a folder whit some kind of whack name like gr589jdw.slt in this folder your settings are stored. your bookmarks are in bookmarks.html
Dunno about win98. probably somewhere in the windows dir. You should search for a dir called Phoenix.
I have used mozilla 1.3 on both windows and linux, and I just copied this complete folder with my settings from windows to linux, so the settings are the same. However,I didn't sucseed in letting them use the same folders, since windows uses \ while linux uses / in path names, so the config files didn't work. But maybe whit some work it can be done.