He COULD play around with the MTU but that's not really going to slow down a 1.5 meg connection. Probably won't even phase it. The only thing that it will, for sure, do is make file transfers from one computer to the other an absolute nightmare.
Playing with the MTU is going to throtte back the whole NIC, not just the internet connection. But like I said, I don't think it will slow down the 1.5 meg or whatever his broadband connection is. It will still squeek through.
I can understand his frustration. I have 4 computers on my network, one of them being the FTP/Web/Email server for my domain. I had to put time limits on the FTP so I could play my game without interruption. But it never fails. I'll be layin a whoopin on everyone and the wife will sneak on her computer to surf QVC.
Man that's annoying. Like there's anything more important on QVC.