STEAM Question - Disk Storage

[Housey]

I have a couple of Intel Gen 2 SSD's in my games PC as well as 3 normal drives. I have STEAM installed in SSD 1 and I then install any games onto SSD 2 or other normal drives. I have just tried to re-install a backed up STEAM game and it tells me I don't have enough disk space. The place I intend to install the game has plenty but I imagine it relates to SSD 1 where the STEAM application is stored which only has 10GB left and it suggests it need 11GB. Now if it's not actually installing the game on SSD 1 how can I get around this and is there somewhere that STEAM stores it's downloads, which I can now delete as I have the games backed up on my NAS.

Thanks in advance.

 

[Housey]

For clarity chaps:

Drive C: (SSD 1) is where STEAM is installed.
Drive D: (SSD 2) is where all STEAM games are installed.
Drive E: (Raptor) is where non STEAM games are installed.

The issue is I am trying, using a backed up STEAM game (Total War) to re-install it to D: where I have space but when I click on the STEAM Backup it does not let me select where I want to restore it to from what I can see. I have plenty of space on D: for the game, but C: does not have space and it seems to be forcing me to install it on C: or needs to see space on C: before it gives me the option where to install it.

 

[Housey]

I have just double checked guys, seems I am somewhat at odds with what I thought. Checking the 2 games on D: (SSD 2) that I thought were the games installs, they are in fact simply backups (BFBC and Bioshock2). It seems that they are all in C: (SSD1) unlike I thought.