The general procedure is one I'm sure you've seen:

(1) In a new tab, type or paste about:config in the address bar and press Enter. Click the button promising to be careful.

(2) In the search box above the list, type or paste newtab and pause while the list is filtered

(3) Double-click the browser.newtab.url preference and enter your preferred page:

• Page thumbnails (default) => about:newtab
• Blank tab => about:blank
• Built-in Firefox home page => about:home
• Any other page => full URL to the page

Press Ctrl+t to open a new tab to test:

Is it fixed for the moment?

If it reverts when you exit and restart Firefox, it could indicate that you have some software on your computer that is protecting you from unwanted settings changes, but also preventing you from changing them yourself. I don't know whether AVG does that, but Advanced SystemCare's surfing protection feature, for example, can do that.

To get your pinned sites back, we have to do a little digging. The reset feature should have created a folder on your desktop named Old Firefox Data. Can you find that?

Assuming yes, click into it and you should find your old settings folder containing your list of pinned sites. We can extract that and insert it into your current settings. Here's how I suggest doing it.

(1) Find the prefs.js file. If you find a file named prefs that does not have the .js extension, to confirm that it is the correct file, change the Windows setting that hides file extensions. This article has the steps: http://support.microsoft.com/kb/865219.

(2) Open the prefs.js file in a text editor such as Notepad. Please note that double-clicking the file will generate a script error. You probably will need to right-click it and use either Edit or Open to open it up.

(3) Search for newtab and look for the line that resembles this (except that ... will be your list of pinned sites):

user_pref("browser.newtabpage.pinned", "[{\"url\":...}]");

This has the data you need. Select and copy the part starting with [{ and ending with }] .

(4) Back in Firefox, open up about:config and filter the list using newtab (again). Find browser.newtabpage.pinned, double-click it, and paste the list that you copied from the old prefs.js. Then OK that. Try Ctrl+t to see whether it worked. Any luck?