The following steps worked for me:
1. Check Windows Key registry: there MUST be a "HKEY_LOCAL_MACHINE\SOFTWARE\Electronic Arts\EA Games\Battlefield 2\ergc" containing xKEY as data(KEY being your KEY without dashes)
2. Change computer date to a date in the future
3. Use the key change tool + Manually changed that registry data to my own key. (just to be sure)
4. Run BF2.exe till menu screen
5. Change date back to current date
6. Run PRLauncher.exe and my key hash changed!
EDIT:
My key hash changed, but I still get the error that my key is invalid