None of the programs in Arduino example is compiling
A couple of things here look odd – but then I don't use Windows very often – I'd suggest that you download a fresh copy of the stock (not development) Arduino IDE. You can get it here.

What's odd looking too me is:


The double backslashes, they could be causing the file to appear not to exist, and
The arduino-nightly component in the path. That suggests to me that you're using a "bleeding edge" version of the IDE where problems are likely to creep in. These versions are for developers and people who like living on the edge (or who want to help with testing new features and the like).


One thing to do to check out the first oddity is to actually try to follow that path (both with and without the double backslashes). If the file is there (without the double backslashes) then it seems like something is odd with the path construction in the IDE.