You will need Windows 7 *SP1*, as I don't think VS will run without the updates. There is also a service pack for VS 2010 that may enable opening the newer solution - it certainly worked for me.

We decided not to keep the old project files as they weren't being maintained.

Community edition is free, but you need a Microsoft account (also free) to register it. I don't know why this is necessary, but that's the way they set it up.

I'll check out that buildbot when I get a chance (Trent's one is known to be busted). The stable buildbots and the one with VS 2015 were doing fine last time I looked.

I haven't tried with the SDK compilers, but it should be possible to build with them now. VS is no longer required to build from the command line.