Desktop Lock click here, or something similar should do, but it costs £24.95 - around £13-14. I think it comes with a 30-day free trial, so worth a free try I suppose. If I find a similar free program, I'll be back to post it.
In meantime, to the solve the broken downloading problem, you could use a free tool like Star Downloader click here, which will resume downloads from the point your Internet connection was cut off. G