If the CAB file can be opened with Windows Explorer or another extraction software, you may be able to manually restore the backup. Here are the steps to do so:

1. Create a folder called Test.SAJ.
2. Open the backup file by double clicking on it.
3. Select all the files in it (CTRL-A) and then right click and choose Copy.
4. Go to the Test.SAJ folder that you created earlier.
5. Right-click and Paste all the files into it.
6. Create two new folders in the Test.SAJ folder named mysql and simply.
7. Change the view in the folder to Details.
8. Order the files by name.
9. Move the 18 sets of groups of three files that end in .MYI, .MYD and .frm to the mysql folder.
10. Move all remaining .frm files and the file db.opt to the simply folder.
11. You should now have the two folders (simply and mysql) and five files (iblogfile0, iblogfile1, ibdata1, errorlog.txt and your Sage 50 Data File). You may have other foreign files like backups which you can remove from this folder.
12. Move the Sage 50 Data File out of test.saj and place it beside that folder.
13. Change the name test in test.saj to match the name of your Sage 50 Data File. eg. if it was Acme Industries 2013, rename test.saj to Acme Industries 2013.saj
14. Make certain that none of the files or folders are hidden inside the SAJ folder and attempt to open it with Sage 50.
15. If it opens, you're in business. If it doesn't, contact Sage 50 Support at 1-888-522-2722.