sharing Thunderbird local folders/ write permissions to vfat partition

[jason]

I have a dual boot XP/Fedora with Mozilla Thunderbird running on both. 
I'm trying to make it so that the Local Folders are available to both. I 
moved all my files from my Local Folders onto a vfat partition. This 
partition automatically mounts in FC1. I changed my Local Directory in 
XP and FC1 to the location on the vfat partition.

Works fine in XP. In FC1 the first time I opened the Local Folders I 
could see all my mail, but I could not filter mail from my imap server 
to the local folders because of write permissions. I tried changing 
permissions through the nautilus gui kdesu'd in but it wouldn't let me 
change permissions. Why can't I change these permissions even as root; 
is it because the drive is already mounted? I tried changing /etc/fstab 
but wouldn't let me change the permissions here (even after reboots). Am 
I trying to change write permissions in the wrong place? After this I 
could see the folders in thunderbird but could not see any of my mail. I 
changed /etc/fstab to defaults and still see the folders but still 
nothing in them. When I look to see what's mounted it shows read write 
permission to this partition, but is that only for "root" which 
automatically mounted the partition on boot up? Booted back into XP and 
it sees my local folders on the vfat partition just fine.  Again, I see 
the folders in Thunderbird but can't read or write messages.

Maybe this is more of a Thunderbird question but I thought there might 
be a Linux/Fedora specific component/fix to it.

--jason

PS I'd found these instructions for dual boot with mozilla mail if 
you're interested in trying it yourself: 
http://vsbabu.org/mt/archives/2003/07/06/mozilla_mailbox_in_dualboot_machine.html