Hey!! Well.. I don't think that they are tampered in any way. Please download the following files: SteamEmu CF Toolbox UCL 1.1
First, you need to install UCL 1.1. Then you extract what is in side of SteamEmu.rar in to the UCL 1.1 Installation folder and replace the file inside of it. Run UCL 1.1 once and you will see a SteamApps folder then. Move your GCF files for Portal in to that folder. To see the game in UCL, you have to click one of the menus at the top and something about refreshing the list (i forgot..).
CF Toolbox is a program to check your GCF Files to see if they are original/updated. CF Toolbox could also download Steam files.
If you need any more questions/help, just PM me!
BTW!! I added the above stuff just if you need them
I never used those GCFs... I need some help. I downloaded The Orange Box torrent with these folders: Source2007GcfAll, Portal, Half-Life2EpisodeTwo and TeamFortress2. Each folder have in it some GCFs files. I tried to put "Source2007GcfAll" GCFs in SteamApps folder, and I tried to put "Portal" in SteamApps and SoureMods. I opened UCL, refreshed, and all I got in the list is "Steam". No "Portal" or anything...