Update:
Plan B:
OK you say it didnt work.... this is kind of a long shot but saved my bacon a lot when I was working as a technician in my past life and had to find unknown device drivers.
Right click your Nexus in device manager , select properties and go to this page
The example shows my radeon card but if you google this hardware ID( the top one in your pc), and check a couple of random sites , you are likely to find it. This method is used for finding unknown drivers, and you may as well give it a shot as you have exhausted most options.
Plan C:
Trying the same nexus on a different windows7 computer to see if it installs . If it does, then you can try to extract it from that computer ( e.g. using driverguide software) and force windows on your main pc to use that.
Plan D:
run sysprep.exe on your PC by typing it in RUN and double clicking the file and clicking Generealize.This prepares your pc for imaging and removes all drivers. Note that you'll have to activate windows again after this.
Plan E:
And lastly, the call center answer , use system restore, although the damned thing fails 90% of the time and install again after a reboot. or a whole scary reinstall of windows :(
//Ignore below now as it didn't work for you
Download this driver http://www.samsung.com/us/support/owners/product/SCH-I515MSAVZW
You can also check this question for a solution for Nexus and an alternative driver. I had the same problem , although not with a Nexus, but a sony Xperia, and I had to download a generic driver to get it going. The above samsung site has the driver, but the model is called SCH-I515. You should be able to fix it without the generic driver
ADB dosn't recognize my Galaxy Nexus - Win7
