It would be more complicated using Firefox Portable that when using the official version of Firefox. By default, the official version would have a separate Profile for each Windows Logon User Account. The "Profile" is what makes Firefox unique for each user; bookmarks, passwords, browsing history, and similar. Whereas, with Firefox Portable the Profile would be in the same folder as where the Firefox program files were installed. Then each user would need to create their own Profile, which is far more difficult than with the official version. BTW, Firefox Portable support is over here: http://portableapps.com/forums/support/firefox_portable