The Program Files folder is where the 64bit programs will install their regular program files, the program files (x86) is where the 32bit programs will install theirs. Some programs will actually install in Both folders, depending on how they're setup but that's not too often. You'll see 2 Win Media Players because both a 32bit and 64bit version are present, and other Windows program folders like Defender, Collaboration, Mail, NT and others all have folders in both as well even tho they don't have 2 version like WMP does.
It's easy to add your old drive to the new system, just install it as usual and it'll be detected and installed like normal.
I have a little reg file for you that adds 2 more options into your right click context menu, Add to Folder & Copy to Folder. These are indespensible commands that should be there to start but aren't. Once you use them you'll understand why many 100's of us have this tweak installed...
Don't drag stuff, that's sketchy at times. After installing the attached reg file, just use ctrl+a to select all, then right click on ay one of the selected files and choose either "Copy to folder" or "Move to folder" and then nav to the folder you want them to go too.
Extract the attached zipped file to your desktop and dbl-click to install it, you'll never regret this one, it's the first thing I reinstall after I reinstall..