If the demo was recorded on a server that streams it's logs here then send it to the admin of the server and get them to submit it. If the demo was recorded on a server that wasn't streaming then there's nothing you can do with it.
That GUID is already on the PBBans MBI clickme. You should also know that PBBans wont ban unless the server is streaming it's logs here.
Have a read http://www.pbbans.com/info-center-starterguide.html
What's your new GUID ?.. You'll need to put your new key back in to find the following out.
Go into game, drop the console and type /pb_myguid (press enter)
Now type /condump GUID (press enter)
Exit out of the game, In the base/mp folder will be a file GUID.txt, open that and copy paste the contents here or pm me it if you don't wan't it public.
As the GUID is banned on the new key then yes, It's useless, blame Activision for that.
Your old GUID/Key 3d1842c59d5d74f0de6529141492f704 (first seen - Jul 24, 2006 / last seen - Jan 28, 2009)
is not on the PBBans, Punksbusted or Game-violations banlist nor is it global banned by EvenBalance, so...
Would suggest the Admin of that server has banned you.