what you need to do is goto start, run : regedit
click the +on HKEY_CURRENT_USER
then click + on software
then + on valve - half life - settings and key should be about half way down...KEY. double click it, should pop up a box, thats where you change it.
you just input your new one there.. K
has to be a valid one other wise your hl wont play...:yes: