I have had a Series 2 for 10+ years. Purchased a second series 2 from weaknees a week or so ago. It was purchased with life-time guide subscription service. I cannot use TivoToGo to get programs from the new weaknees Tivo because the media access key does not match my old Tivo's media access key. When I tried to go to Tivo's site under manage my account it shows no DVR's under my account with the message "There are no active DVRs associated with this account".
I at least want to be able to use TivoToGo to get programs from the newer weaknees Tivo to my PC and at best transfer shows from one Tivo to the other. Can I contact Tivo (or do I need to) to put the new weaknees Tivo service number into their system to be able to enable transfers between the two Tivo's?

You just need to contact TiVo and ask them to put this new unit on your account.

Then your Media Access Keys will match.

Just a sincere "Thank You" for your help... contacted Tivo and all went well... Can now transfer Tivo recordings from both Tivos to my PC as well as transfer recordings between the two Tivos. I was concerned about contacting Tivo about my new(er) Weaknees Tivo unit since I did not buy the lifetime subscription through Tivo directly but through Weaknees with the refurbished Tivo unit. Are there any got-ya's as far as future purchases of used Tivo units if I should decide to purchase one in the future through let's say E-Bay and they advertise it as "includes lifetime subscription".... how (if possible before the purchase) can I be sure that the unit in fact includes (has been purchased) a lifetime guide subscription? Any reply would be appreciated and "Thanks Again" for your assistance.

I would caution against buying units on eBay with service unless they are from a reputable TiVo dealer or you know the history of the unit.