Been meaning to put this on the new mohaa site. Maybe it will catch murdo's eye and he'll add it.
Seems to be that when you install Spearhead on certain machines and try to play the game, it will report something like "No CD". I'm not sure if this happens with other expansion packs, but heres the fix:
Go to start>>run>> regedit
Work your way to:
HKLM>>Software>>EA Games>>Medal of Honour Allied Assault>>18.104.22.168
Rename to 22.214.171.124
Now try reinstalling and all should work...you may not even have to reinstall.