There are a few steps to try.
First, try resetting Firefox: https://support.mozilla.org/en-US/kb/reset-firefox-easily-fix-most-problems
If this doesn’t solve the problem, trying using the Firefox Profile Manager to remove your old profile and create a new one manually:https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles
If this still doesn’t work, try deleting the profile.ini file to force Firefox to create a new default profile:
Make sure that Firefox is closed
Press Windows key+R to open the Run box
Delete the file called “profile.ini”
Run Firefox again
3. After pasting the above commands, please click File on the menu and click Save.
4. Type in NewFolder.reg as the file name, select to save the file on the Desktop. Click Save.
5. Go to the Desktop, and double click NewFolder.reg. A dialog box will pop-up saying "Are you sure you want to add the information in fix.reg to the registry?". Click Yes to confirm.
Go here: http://www.stardock.com/products/iconpackager/
and get the trial version of IconPackager, install it, use it to switch to any icon package, then switch back (if you want to) the standard windows icons.
And voila... all icons back.
Please try the instruction below.
Step 1: Start the Windows Installer service.
a. Click Start, type Services.msc and press [ENTER]
b. Double-click Windows Installer.
c. Set the Startup type of Windows Installer to Manual.
d. Click Start to start the service. Note down the error message if any.
e. Click OK.
Step 2: Install the latest version of Windows Installer which you can download it from the link: