1. Win---> Run ---> Type "regedit" and press Enter key
2. There, go to this path.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Keyboard Layout
3. Select 'Keyboard Layout' and Right click. Then choose 'New' and then 'Binary value'.
4. Then you will be automatically get prompted to change the name of that newly created binary value. Give it the name 'Scancode Map'
5. Then right click on that newly created 'Scancode Map' and choose 'Modify'
6. When 'Modify' window is opened, give the below value to 'Value data' in it,
00000000 00000000 02000000 44005BE0 00000000
7. When you entering above value, some extra numbers and symbols will automatically appear in left and right sides of above value. Don't worry about them. After entering above value press 'ok'.
8. Close 'regedit' program, and restart computer.
9. That's all. Your Win left key will now work as F10. (If you want Win right key to be your F10, you should change 5BE0 of above value to 5CE0)