Amazon Server

An old customer emailed me about moving his MS Access database application onto Amazon's web based cloud server. This is a distributed package with the program on the front end, and data on the back end.
I know nothing about cloud computing. I'm guessing that I would have to convert the back end to SQL Server tables. I think the user envisions his people to be able to access the database from the field, doing reporting and creating forms to be given to customers. I assume he wants multiple users to have access at the same time.

Is this a possibility without a major program re-write? Can we just give the cloud database a drive letter and map it from the front end? Or is this just a pipe dream and is a web-based application the way to go? If that's the case, we're talking big money and the idea is a bust.