Sen and K3d brought this to my attention but I thought I would share the information with everyone else for this useful little windows feature.
It boils down to running two hard drives and having your main running out of space.
Personally I'm running a 60GB SSD and another drive for other stuff. The 60GB runs out of space painfully quick when downloading games. For a while I was copying steamapps folders from one to the other everytime I wanted to play a different game. It was a pain in the arse.
So whenever you install a game on steam ( that isn't a valve game ) it will go to something like C:\Program Files (x86)\Steam\steamapps\common\gamenamehere
What you can do is create a junction round this whole folder using the command prompt.
First you will need to create the folder where you want everything to go on your other hard drive say D:\SteamJunction\
Then copy the common folder over to the new folder you created.
Then delete the one from the C drive ( if it exists in the original location then apparently it doesn't work).
Open the command prompt from accessories and right click it to run as administrator.
This is the magic command ( make sure you close steam before using it) :
mklink /J "directory to where your common folder should exist" "directory to where you have copied it"
i.e.
mklink /J "C:\Program Files (x86)\Steam\steamapps\common" "D:\SteamJunction\common"
If you now go to C:\Program Files (x86)\Steam\steamapps\common it look like a shortcut and you can open it and navigate the folder and windows will say that its still on the c drive and not on the d drive where the files actually are.
You don't have to do this for the whole folder you can do it for individual games i.e.
mklink /J "C:\Program Files (x86)\Steam\steamapps\common\killingfloor" "D:\SteamJunction\killingfloor"
This works for windows 7 and should work for vista as well. I'm not sure about xp as I know that some of the command line functionality changed when vista was launched. Here is a post on the steam forums:
http://forums.steampowered.com/forums/showthread.php?t=664376
For anyone not used to the command line the tab key auto completes what you are tying so say you type C:\P hit tab and it will start completing everything that begins with what you typed till you get to C:\ProgramFiles then rinse repeat.
any questions? no? good
