Chrome, Opera, and Pale Moon are good browsers for you if you have a decent computer, but if you have a slow one, I would recommend Pale Moon Atom-Optimized, Maxthon, SlimBrowser, or SlimBoat (Pale Moon probably has the most features out of all of them, and Maxthon comes in second place because of its speed).

Have you tried performing a clean reinstall of Firefox?

Note: You might want to print these steps or view them in another browser.

1. Download the latest Desktop version of Firefox from mozilla.org (or choose the download for your operating system and language from this page) and save the setup file to your computer.
2. After the download finishes, close all Firefox windows (or open the Firefox menu and click the close button ).
3. Delete the Firefox installation folder, which is located in one of these locations, by default:
   • Windows:
     • C:\Program Files\Mozilla Firefox
     • C:\Program Files (x86)\Mozilla Firefox
   • Mac: Delete Firefox from the Applications folder.
   • Linux: If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it - see Install Firefox on Linux. If you downloaded and installed the binary package from the Firefox download page, simply remove the folder firefox in your home directory.
4. Now, go ahead and reinstall Firefox:
   1. Double-click the downloaded installation file and go through the steps of the installation wizard.
   2. Once the wizard is finished, choose to directly open Firefox after clicking the Finish button.

More information about reinstalling Firefox can be found here.

WARNING: Do not use a third party uninstaller as part of this process. Doing so could permanently delete your Firefox profile data, including but not limited to, extensions, cache, cookies, bookmarks, personal settings and saved passwords. These cannot be easily recovered unless they have been backed up to an external device! See Back up and restore information in Firefox profiles.

Also, Firefox might not run well if your computer is outdated. The minimum amount of RAM required to run Firefox is 512 MB (half a GB), but realistically, you would want to have 1 GB. You have Intel HD Graphics, so the oldest CPU that it is possible for you to have is Intel Core i3. Therefore, an old CPU is not the problem.

Perhaps you need to defragment your hard disk drive. An guide on how to defrag is located here: http://windows.microsoft.com/en-us/windows/improve-performance-defragmenting-hard-disk#1TC=windows-7