Call up DirecTV and talk to a CSR. Be prepared to give them the Serial number and RID number of the old receiver and of the R10 DVR. You MIGHT be able to have the present card activated in the DVR, but don't bet on it. And if the previous owner of the R10 owes money, you are pretty much SOL unless you want to pay off his old bill. Subscribing it will add about $8 to your monthly bill.
There's a difference between needing help, and just being plain ole' lazy.
"You cannot teach a man anything. You can only help him find it for himself." Galileo Galilei (1564-1642)
HR20-700 with 2 TB, HR22-100, HR22-100, HR22-100, HR23-100 all running 0x5cd and networked.