I have several computers at different locations, each with their own copy of an MS-Access 2007 front end. Each copy links to an SQL-Server 2008 back end on a server. I would like to migrate the back end to Sharepoint and have each front end access it there. IS this possible, or do I have to use Azure? I would also like to know if its possible to have both front and back ends on Sharepoint, and have my users operate with thin-client workstations? If any of these two options are possible, please explain how I can go about implementing them.
The scenarios you could use with SharePoint are:
Save the database file in SharePoint itself and check it in and out when you're using it just like you'd do with any other file. This is kind of rickety and SP isn't really going to do a great job of telling you what changes you made, but it's possible, I guess.
Use Access Services to, in essence, host the Access DB on SharePoint itself. Your SharePoint WFEs then are going to become the WFEs for your Access database. This is still not quite the same thing as what you're doing at the moment; while the tables/views/etc. will be stored within SharePoint, they'll be stored the way SharePoint stores objects, with all the normal SharePoint DB caveats attached (if you edit the data therein directly via a stored proc or something you could kill the entire SP farm, MS doesn't support accessing the DB directly, and so on).
Depending on how advanced your database architecture is, you could use a BCS connection to the DB in question and then render the tables or views you want to access as SharePoint lists. So long as you get the SQL calls right, they'll look like regular old lists on the front end and behave like a database on the backend.