New HD installed with Snow Leopard, need to restore Tiger

This is probably obvious to you all, but having done a disasterous restore once in my life I don't want to take any chances. One of the computers I work on is a 15" MacBook Pro 15" pre unibody - Intel Core Duo. I bought it second hand to replace a Quicksilver tower and was delighted to have Tiger on it since we use Adobe CS2 and it was hinky on Leopard. OBviously not springing for CS5 anytime soon unless someone gives me a lot of money. So I need at least 1 computer running Tiger. My HD crashed and I decided since I was in a rush to let Apple replace the drive for me (the 23 screws were a little daunting to me while under a wee bit of stress). The computer came back with Snow Leopard installed. I have my (bootable) clone on an external HD and want to restore - do I need to erase (reformat??) the hd before the restore or does CCC erase for me? As I said I did this wrong once . . . . and, pathetic as it is, I am the computer wrangler in this establishment, so I am counting on you!

Thanks

Annexit