Answer 1
Hi WK,
You might need to upgrade the solutions to make them work on sharepoint 2010.
For example, some MOSS 2007 solutions are developed for 32 bit platform and SharePoint 2010 supports 64 bit only, so an upgrade is necessary.
Please take a look at this video for how to upgrade MOSS 2007 solutions to SharePoint 2010.
http://channel9.msdn.com/posts/matthijs/Upgrading-your-SharePoint-2007-solutions-SharePoint-2010/
Hope it helps.
Thanks & Regards.