[pointyhats]

The Windows kernel is C++. From what I've seen (shared source), it's mainly C-style C++ though. I didn't see a single template or a class in my travels.

[munin]

If you read the WRK, ntoskrnl is all C...

[pjmlp]

Or a C++ subset in the near future, if the BUILD 2012 remark is true.

[malkia]

and most of all extern "C", possibly no exceptions, no RTTI, no global new/delete, etc. - e.g. "embedded"-C++ like (only guessing).

[pjmlp]

Most likely yes.