Is it possible to install Windows 7 on Retina MacBook with a shared CD drive?

• My school provides Windows 7 Ultimate upgrades to students
• My friend installed Windows 7 normally even though it's technically an upgrade (burned the .img file to a DVD using Disk Utility and installed it through the Boot Camp Assistant tool in Snow Leopard)
• I own a 2008 MacBook which has an optical drive
• I own 1, 2 GB thumb drive and 1, 4 GB thumb drive

Is it possible to install Windows 7 through my Retina MacBook Pro through a shared CD connection with my 2008 MacBook?

I tried using the Boot Camp Assitant tool.

• I burned the Windows 7 upgrade .img file to a DVD with Disk Utility just like my friend
• I copied that DVD as a .cdr file to my Retina MacBook using the shared CD connection and Disk Utility, and changed the file extension to .iso
• With the Boot Camp Assistant, I set-up my 4 GB thumb drive
• When I get to the "Create a Partition for Windows" screen and I press install, I get the message "The installer disc could not be found".

The DVD is in my 2008 MacBook and I mounted it on the Retina MacBook. The 4 GB Windows set-up thumb drive is connected to the Retina MacBook.

I'm confused as to what I'm doing wrong.

Any help is appreciated.