I have made a (barely) portable version of Counter-Strike: Source. I say barely as it only fits on a 4GB drive with compression turned on (I use NTFS). Due to both legal and logistical concerns, I cannot post the file, but I would like to provide instructions for those curious as to how to do it.
Before you begin, you should get a copy of 7-Zip (portable is a plus). This will be needed for getting some of the necessary files out of the installer.
First, you should download, but not run, the Steam installer from http://www.steampowered.com/v/index.php?area=about&cc=US . After downloading the file, find it in 7-Zip. Right click on it, and select the open inside option (double clicking may not always work). Then extract the "Steam.exe" file to anywhere, preferably a designated folder, but must be on your hard drive or some other LARGE drive, as it will be spawning ~30 more files into the directory where it is located.
From here on out it is much more straightforward. You can even multitask a bit:
I. Run Steam.exe and let it update (it will take a good bit). Once it is done updating, install Counter-Strike: Source by method of choice:
a. Download the files through Steam: This is the least complicated, but may take some time if you have a small amount of bandwidth.
b. Copy most of the files from a previous installation, and let Steam do the rest: You will want to copy the following .gcf files that are located in the steamapps directory:
base source engine 2.gcf
counter-strike source client.gcf
counter-strike source shared.gcf
You should also copy the contents of your steamapps\username\counter-strike source folder.
Then rerun Steam. It should claim that it is 100%, but it might go through an update process to get some other small files. (It has been awhile since I made my build of CS:S:P, but this should pretty much do it.)
c. Install by CD: This is almost identical to the previous method, but requires much less fiddling with files, as well as no previous installation of CS:S on that computer. Simply install the game as normal, making sure that the install directory is that of the soon-to-be-portable steam. (There is some way to fool the CD installer into thinking that there is no CS:S installation on your machine, but I do not know what it is, I simply know it exists because I installed CS:S to an external hard drive, removed the drive, "uninstalled" it from the CD, and then reinstalled it to the new Steam. I suspect that it is a registry entry.)
II. Format your drive to an NTFS with compression on, or some other format with built in compression. It will not fit on a straight 4GB stick, even with UPXing, because Steam will complain about not having elbow room. Touchy, touchy...
After both I and II are done, you can then move your folder to the drive. THIS WILL TAKE AWHILE. Go get some
coffee or tea Mountain Dew and sit back. Then, when it finishes, tada! You now have CS:S:P. Here are a few suggested upgrades:
* autorun.inf - This makes it look REALLY NICE when you plug it in for your friends. One even asked me where I bought CS:S installed on a memory stick! Simply make a file called autorun.inf in the root of your drive, and put the following text into the file (use Notepad or similar):
Open="Portable Steam\Steam.exe" -applaunch 240
Action=Start Counter-Strike: Source
Label=Counter-Strike: Source: Portable
shell\play=Play Counter-Strike: Source
shell\play\command="Portable Steam\Steam.exe" -applaunch 240
Remember to replace Portable Steam with whatever your directory for Steam is. Also, I do not know if the "240" above will work for all installations of CS:S:P, if it doesn't work, create a shortcut for CS:S on your desktop and look at the properties for it. For a description of what all this does, I recommend DCoT's guide to autorun.inf's at http://www.dailycupoftech.com/?page_id=149 .
* Shortcuts located in the root directory of your drive are a nice touch as well, and much simpler than the above
That's about it! Please post any comments/questions about this, and I will try to respond in a timely manner.