I also have have a 3700, but that isn't a DVR.I think I have you beat. I have two 512's and a 501.
My guess would be that they do not include the "built in" backup utilities for the PC.BTW, I was in MicroCenter today and I noticed PLENTY of 1TB, 2TB and 500GB HDDs. Around $60, IIRC.
So there are plenty of them still available.
Odd thing I noticed. The ones marked for surveillance camera use were CHEAPER than the others. Why would that be?
I have to say, I'm glad I got rid of those two 7200's I had back in the day. Even got more than I originally paid for them. That has never happened to me before or since with any piece of electronics.
Ha ha. Actually, I was able to fill up the 501 with stuff I wanted to watch, before Dish stopped broadcasting in a format that it can handle. The 512's still work for free preview channels. I have a bunch of Mythbusters episodes on one of them, recorded during a Science Channel preview last year.Are they holding your doors open well?