In order to use Zotero through Portable Firefox on your external drive, you will need to

1. Install Portable Firefox and Zotero onto your external drive
2. Move your Zotero library onto the external drive
3. Specify the location of your library in Zotero

Install Portable Firefox for Win or Mac according to the directions. Then, run Portable Firefox and install Zotero. (The latest version of Zotero is available from the home page.)

Zotero stores everything on your computer in a subdirectory of your Firefox profile directory. In most cases, you will find your Zotero files here:

On a Mac:
/Users/<username>/Library/Application Support/Firefox/Profiles/<randomstring>/zotero

On Windows:
C:\Documents and Settings\<username>\ApplicationData\Mozilla\Firefox\Profiles\<randomstring>\zotero

On Windows Vista:
C:\users\<User Name>AppData\Roaming\Mozilla\Firefox\Profiles\<randomstring>\zotero

You can also locate your data directory by going to the Zotero preferences under the Actions (gear icon) menu and clicking “Show data directory” on the Advanced pane.

With Firefox closed, copy this directory onto your external drive. Remember the location for step 3.

Open the Preferences Menu in Zotero/Portable Firefox. You can access Preferences either from the Actions () menu in the Zotero pane or through the Firefox Tools menu → Add-ons window (click the Preferences button in the Zotero section).

• Click on “Advanced” in the Preferences Menu
  
• Click on “Custom” under Storage Locations to specify the external drive location of your Zotero library. The “Select a Zotero Data Directory” pop-up will appear. Once you select the directory, Zotero will restart Portable Firefox with the contents of your library.