HUH? Well you should just copy the files from your one computer you installed it on, and move them to your laptop through a network.
I have had problems with HL2/Steam lately and luckily I had a backup copy and just copied it over through my network and things worked out.
So basically take you VALVE program files folder and copy it over to you laptop. It shouldnt need any registry files to work. If you dont have a network then ummm....
Also make sure you arent connected to the internet.
and what does it say when it wont let you install it?
