Whew...close call.
I have been concerned about the consequences of losing power to my 8300 and external hard drive given the ominous warning message displayed when first connecting and formatting the external and the minor problems I had initially getting it working (it required me to have the hard drive powered up and spinning prior to powering down/up the 8300 (i initially had the external hd connected to the outlet port on the back of the 8300 but that wasn't working)). Anyhow, the wife (or the kids, but they blame my wife

) for some reason powered down my surge protector/line conditioner which caused my 8300 and hd to lose power. I was petrified that since it wasn't powered down and disconnected in accordance with the message displayed by the 8300 that I was going to lose all the programming that was now sitting on the external 400 (which btw i managed to fill up in about a week since install). So, I hit the power switch on the surge protector/line conditioner, observed the external hd and 8300 power up and waited to see what message would be displayed on the screen.
Thankfully, the 8300 went through a normal power up, never displaying any kind of message about the external drive, and when I instructed it to list the DVR programs, everything was there just as I left it!!!
I guess I should be able to put together another one of these and swap it out with the existing drive if I wanted to have a library of material (understanding that it isn't a stable archive since it is married to that particular 8300 and authorization card combo).