The path being called is the unix path. You are using a windows installation. You need to edit the globals.php to point to the correct path of your mysql (and other tools) for this to work on windows.
on XAMPP, assuming you installed it on the C: the path would be c:\XAMPP\bin\mysqldump, if XAMPP is added to the Windows PATH environment variable you can skip the pathing and just use the binary name.
The temp needs to be configured as well.
Hope that gets you pointed in the right direction.
-Tony
The mysql error 127 says that the table(s) might be corrupted. Just try checktable/Repairtable from the phpmyadmin itself. If the table is corrupted, the status will be shown and you can do Repair table.
The backup process need only the /tmp access by default and nothing to do with globals, if the application is running properly.