I use a regular Firefox install on my PC, and Firefox Portable on my USB. On my PC, I moved the C:\Users\\Appdata\Roaming\Mozilla folder to a separate partition, and used the mklink command in Win7 to symlink it. All worked fine until I ran Firefox Portable on my PC... When it exited, it deleted the symlink. This is the only portable app I've used that deletes symlinks. I've done the same thing with Pidgin's .purple folder, Thunderbird's folder, etc, and those portable apps don't mess with my symlinks.
http://lifehacker.com/5358983/use-dropbox-for-more-than-just-file-syncing
section Sync Your Pidgin Profile explains about the symlinks if you don't understand what I'm talking about.
Why does Firefox Portable delete the symlink on exit?
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Firefox Portable deletes symlinks
September 16, 2009 - 10:54am
#1
Firefox Portable deletes symlinks
The simple reason is because they don't work right. The launcher is set to delete that folder if Windows reports it as empty using the RMDir command within NSIS. Specific calls in Windows report symlinks as empty because they are tacked on to NTFS as an afterthought and don't, in fact, contain any files. Windows reports it as empty. The launcher removes it.
The solution is not to use symlinks in the middle of your Roaming folder. You should set your whole roaming folder as a symlink.
Sometimes, the impossible can become possible, if you're awesome!
When I use Windows Explorer a folder junction (symlink) looks just like a folder,
and if I delete that symlink the folder disappears,
UNFORTUNATELY everything that was designated on the other side of the symlink is also deleted.
It is a mild inconvenience if the symlink has to be recreated with 3 or 4 mouse clicks,
but it is catastrophic if a major set of data has been destroyed.
Regards
Alan