custom ASPX pages with webparts upgrade to 2010

when upgrading to 2010, how can we upgrade our custom ASPX pages?

we have a new server set up with 2010 on it.   And I've tested restoring our Content databases to the new sharepoint 2010 server.   One issue we see is that the custom pages aren't displaying.  These are ASPX pages that were created in sharepoint designer.  when trying to view the page on sharepoint 2010, the data view webparts are displaying "Unable to display this web part...correlation id..."

Is there a way to upgrade these or do they have to be rebuilt in SPD 2010?  I'm hoping not rebuilt because we have several of them.

When I open these SPD 2010 they still show version 12 instead of 14 at the top of the page in the page headings/references.   I would think after upgrading the database on the 2010 server, shouldn't it upgrade references in pages and everything to the 2010 formats/controls?

thanks!