As our company would never let a third party like github anywhere near our source code, is anyone aware of any software or setup guides or blogs on how to setup a scm server
I'm not sure what you are looking for but you might not need a web interface.
You could also create a linux server and run git-deamon on it. Then you could use ssh to restrict user access. It is also possible to just create a network share and rescrict access that way.
There are lots of web interfaces for browsing, but I have found none that would run on window out-of-the-box, that could also create/modify a repositorie. A lot of the web interfaces just won't work in windows. Or maybe I didn't looked hard enough... As mentioned before InterfacesFrontendsAndTools is a great source to start looking.
The only stumbling block I can see will be the windows Tortise SVN users having difficulty with the Git windows alternatives
Try GitExtensions, it is very easy.