Faced with the task of testing the leftover bandwidth capacity for 100+ locations multiple times a day, I asked myself if there is some sort of software package you can install on these computers and have them make upload/download tests, then report back to a central server automatically. Does anyone know of a solution that can do that? Bonus points for a solution that runs on Windows and doesn't require me to install extra runtimes.
I was going to provide a rather long and involved answer, but reading your question again makes me think that your interpretation of "bandwidth" testing is radically different from mine.
There is no tool available which does not require you to "install extra runtimes".
Perhaps if you gave a bit more information about how you currently test and what you think it tells you might be helpful.
Certainly I'd recommend strongly that you move away from active testing and use passive testing instead.