Its easy to transfer your Firefoz data from XP to vista or windows 7

• Install Firefox on Vista, launch it once, then close it. Make sure Firefox on XP is closed also
• XP: Back up C:\Documents and Settings\\Application Data\Mozilla\Firefox\Profiles. It should contain only one folder, which has a garbage name.
• Vista Navigate to C:\Users\\AppData\Local\Mozilla\Firefox\Profiles and then enter the only folder in there, which should have a name similar to the one inside Profiles that you backed up earlier.
• Go into the weird folder inside your backup, hit ctrl+A (select all), then ctrl+C (copy)
• Go inside the weird folder on Vista and paste (ctrl+V) all the stuff over the top. As you can see we are just migrating the contents of the weird folders from the backup to the new installation.
• On Vista, go up 4 levels until you get to C:\Users\\AppData. Now go in to the “Roaming” folder, then Mozilla, Firefox, Profiles to get to C:\Users\\AppData\Roaming\Mozilla\Firefox\Profiles.
• Perform the same operation to copy the contents of the weird folder in your backup into the weird folder on Vista