Have a copy of 'The Lost Crown' which I had to uninstall. On trying to reinstall same, I typed in the Reg no as given on the pack but it states I have Cap Lock on (I haven't). Tried all possible combination of the letters and numbers with Cap Lock on and off. Still no luck. Is this a known problem and does anyone have any idea what to try next? Really disappointed as I enjoyed the game very much.

The game may have left entries in the registry (with a Microsoft system) which did not go with an uninstall. You can try deleting these entries.
1) HKEY_CURRENT_USER\Software\DarklingRoom\TheLostCrown
2) HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\MenuOrder\Start Menu\Programs\The Lost Crown
3) HKEY_LOCAL_MACHINE\SOFTWARE\Darkling Room\The Lost Crown
4) HKEY_USERS\S-1-5-21-1844237615-1715567821-839522115-1004\Software\DarklingRoom\TheLostCrown
etc.

Do a registry search and delete the relevant entries.

If my memory hasn't failed me, I believe that the box versions code was indeed case sensitive and you had to use capital letters and include all the spaces, dashes and hyphens, the help sections on the 'darkling room' website also says to use capitals.

I wouldn't suggest going into your registry unless you are very comfortable there - deleting the wrong thing can create havoc. I always use CCleaner on the registry after I uninstall a program to get rid of the registry entries.

Also, rather than use Capslock at all, hold down the Shift key instead when you need to type a capital letter.