[quote name='crunchewy']You can transfer the tracks to DC2, albeit for 400 points, I think it is. It requires a code that comes with DC1 in the case (or possibly in the manual), plus the points.[/QUOTE]
I bought both DC and DC2 right before xmas for $25 each. Each came with a card for 240 points. I redeemed both cards, then used the code on the back of the DC manual and the points to transfer the DC tracks to DC2. Now my DC2 game has twice as many songs, and I had 80 points left over.
Playing DC tracks in DC2, you can play two-player simultaneous on them, just like with the DC2 tracks.