Full procedure for transferring Steam to a new installation:
Download Steam client and install as normal.
Shut down steam client
Copy the following from your old directory:
C:\Program Files (x86)\Steam\steamapps\common (copy all contents or individual games as required)
C:\Program Files (x86)\Steam\steamapps (copy all appmanifest files or for individual games as required)
If you need to figure out what each appmanifest file is associated with use the number on the appmanifest (bolded) as in this hyperlink: http://store.steampowered.com/app/377160/ or open the manifest file using notepad, the game will be ID’d somewhere.
Assuming the directories are stock then thats it. Otherwise open each appmanifest file and edit the “installdir” path to your non-standard location.
eg.
“installdir” ‘Left4Dead’
will install to
C:\Program Files (x86)\Steam\steamapps\common\Left4Dead
but of you want it somewhere different then
“installdir” ‘D:\awkwardplace\justcos\Left4dead’
I think that bits right.
But yeah, it should just be a case of launching Steam and it will recognise everything. I just tried this for Deus Ex in standard install location so it definitely works. Remember to copy over save files as well from your user folder!