To disable a Firefox Add-On follow the instructions below.
1. Click On Tools.
2. Click On Add-Ons.
3. Select Add-On you wish to disable.
4. Click on the Disable button.

To close all open tabs not including the one selected follow the steps below.

1. Right-click in a empty space in the tab bar
2. Click Close Other Tabs

What You Need:
Firefox 3

With Mouse:
1. Click on the Bookmarks button
2. Select Bookmark All Tabs

Without Mouse:
To do this without a mouse in the Firefox use the shortcut Ctrl+Shift+D.

To remove an unwanted add-on follow the steps below:
1.Click On Tools
2.Click On Add-Ons
3.Click On The Extensions Button
4.Click on Add-On you wish to uninstall
5.Click On Uninstall

What You Need:
Mozilla Firefox

Steps :
1. Click On Tools
2. Click On Clear Private Data

Note: To do this without the use of the mouse use Ctrl+Shift+Del.

To change the settings follow the steps below.

1. Click On Tools
2. Click On Options
3. Click On Privacy
4. Click On The Settings button

If you have data that you want to securely delete because you wish to keep the data private then you can use the below method.

Software Needed:
Heidi Eraser (Download at Publishers Website)

Please Be Aware:
Once you erase files you will not be able to recover them.Choose the files to erase wisely.

Steps:
1.Install Eraser
2.Right click on  the file which you wish to erase
3.Select Erase in the context menu
4.Select Options and choose how many passes you wish to do.
5.Click OK
6.Select Yes if you wish to erase