Are you not satisfied from QuickTime X? or do you just want to get Quick Time 7 in your Mac OS X 10.6 Snow Leopard? here is how to do it:

1) Insert the Mac OS X 10.6 Snow Leopard Install DVD

2) Go to the folder "Optional Installs"

3) Open the "Optional Installs.mpkg"

4) Complete the install process

Here is how to do it in video guide:

see video at youtube