Moving System & User Folder drive back to same drive

I have a 2010 15" MBP, with an Optibay setup I installed back when I bought it. The System drive is a 120 gig SSD in the main hard drive spot, and in the Optibay, I have the 500 GB HDD that came with the system, with my Users folder. I also have a Windows 7 installation on a partition on the SSD.

Basically -- I would like to undo this setup. I would like, somehow, to move my System folder, and the Windows 7 installation, to the HDD, get rid of the Optibay and SSD, and reinstall the optical drive. How can I go about this without screwing anything up?

Thanks.

 

I don't mean to be a dunce, but this isn't an issue anyone can help me address?