Maybe use the portable Firefox version on a USB stick if you want to prevent access to your profile.
Solutions that use an extension can easily be bypassed by starting in Safe mode.
Otherwise you need to locate the Firefox profile folder on an encrypted drive.

See http://portableapps.com/apps/internet/browsers/portable_firefox

Thanks for your quick response.

usb stick sounds good but perhaps too cumbersome for daily use. My children wont be able to figure safe mode, so please explain solutions that use an extension? thankyou

Profile Password extension is available here:
http://nic-nac-project.de/~kaosmos/profilepassword-en.html#PPFF

thanks. How can I verify that this add-on is not malicious? who is the-edmeis...

This extension has been around for quite some time and should be OK.

If you do not want your children to access your profile folder or files in your Windows account then you should protect your Windows account with a password and create another Windows account for your children.

You can also create a separate Firefox account for your children and place a link on the desktop and hide your own profile elsewhere in the Start menu. If they are that young that they do not find the Safe mode entry in Start > All Programs > Mozilla Firefox then that might work for now.

• http://kb.mozillazine.org/Creating_a_new_Firefox_profile_on_Windows
• http://kb.mozillazine.org/Shortcut_to_a_specific_profile

thanks for the info.

Its only a lightweight protection I need so that no one mistakenly closes tabs I have open etc

so the password or hiding my profile seem the right solution for me. Thanks again for your help

PS password extension seems to be doing its thing :)

You should make a backup of the file sessionstore.js in the Firefox Profile Folder if you consider tabs that you have opened important or right-click the tab bar and use "Bookmark All Tabs".