have a toshiba hd dvd player (HD-A2KU), need the code to program into my directv HD DVR hr20-700 remote

You have to upgrade your dtv remote to the their latest remote, the rc64rb.

will that remote work with my hr20 -700? it doesnt have the rf plug in the back.

Yes, the only rc64 released so far is the rc64rb, its a RF remote with backlighting. There are like 4 different rc64 remotes to come.

To program it to your receiver you need to enter the last 6 digits of the receiver ID #, to marry the remote to the receiver.

Just order the RF remote off the directv website, don't click the box to add the RF antenna for $5 extra, since the RF antenna is built-in on the HR20-700.

I think my parents have this remote,
does it also do IR?
can I use it to "teach" my learning remote on my marantz sr8001 a/v receiver in "learning" mode to control my hd-a2 player?

Yes it does IR, the only device it will control via RF is the SAT receiver. The toshiba A2 dvd code in the rc64 remote is 21769.

I have the remote that came with the D1-300 receiver.
I tried the above code, and the codes listed in the manual:
[Link: directv.com]

any idea?

The only directv remote models to have a code for the toshiba A2, are the rc64, rc64r, or rc64rb, any other directv remote you're out of luck.

You can also buy an upgradeable "One-For-All" brand universal remote like the urc-8910, 9910, and 9960 and have toshiba code loaded over the phone. In those remotes the code is DVD 1769.