OK, I'm probably the only person who will freely admit that he's tried this.
Why? because I took the pictures in the first look and I had DIRECTV's permission. So I have a bit of advice for you: don't do it.
I'm not going to give you detailed instructions, but I'm going to tell you that it took every flathead screwdriver I had, plus plastic putty knives and folded up pieces of paper. That was just to get the case off. I also removed a bunch of screws that I didn't need to, apparently.
It took me close to an hour to do all this and I darn near broke the front panel several times.
Then I got the thing open and you'll find two things: The drive is secured to the sled with wire and the SATA cable is so short it sits flush against the drive. Look at the pictures in the first look.
It was hard to be sure but the sled might also be soldered in.
As far as 2TB is concerned, I am not 100% sure you can even go up that high with an HR24. I know there are some other members of the HR2x family that won't run a 2TB internal.
My suggestion to you, sir... is eSATA.
And there goes the lust my heart was filled with. No more eSATAs for me.
Thanx for the tip. Saved me a lot of trouble. Great post!