do u know how big the virtual studio installer is? me and maybe another user, were live in country that internet iso expensive and the speed is not very fast is very pain taking.
Then don't run the FSDT Live Update so often, but only when you get a notification there IS an update available.
Also, you are complaining about the Visual Studio installed, because that's what you SEE being downloaded but, the updater is also downloading several files without telling you, and those are REQUIRED for the Live Update to work and they are, guess what, the checksum you are suggesting we should use to make the updater more "efficient", but they are downloaded in the background, so you don't see anything and you don't complain...
can u change the step (algorithm) that can be more efficient with bandwidth and time? maybe you can ask before download (so user take their own risk for not downloading) or you have algorithm to verify checksum the previous downloaded installer with the new one?
Always asking users, would annoy all those users that are not worried about downloading. And having to ALWAYS ask "have you replied YES to the VC++ question ?" each time something doesn't work, would make support slower for everybody.
There's obviously an algorithm to verify checksum for ALL our files, but the VC++ installers are a bit different, because if you already have a newer version, it would fail the checksum, so it would still download even if not required, and it will be only the MS installer that will understand you do have a new version and won't do anything.
So, as I've said, instead of trying to detect your installed version, which is NOT reliable, since you might have the correct registry keys, but your installation might be corrupted/missing files, etc., so it will never, ever, be really foolproof, we just rely in the MS installers doing their job.