Background
I have been tasked to write an application that will be a combination of document and inventory management in VB.net which will be used to store document images in TIFF, PDF, XPS, TXT, DOC, PPT and so on as binary data that can be retrieved for viewing, printing, and possible OCR to be searchable as well along with meta data such as sender, recipient, type of document, date, source, etc. So the table would probably be something like:

DOC_NAME, DOC_DATE, NOTES, ... DOC_BINARY (where the actual document will be put inside)

Help Please
I need help with understanding how to evaluate my database options.

What my concern is finding a database solution that will not become unstable due to size restrictions, records limitations and performance. Some of the options are MS_SQL, SQL Express, SQLite, mySQL, and Access. Now I can pretty much eliminate Access right off the bat as it is just too limiting and not scalable. I can further eliminate SQL Express because of the 2 GB limit and again scalability.

So I believe that leaves me with MS_SQL, SQLite and mySQL (note, I am open to alternatives). And this is where I need help in understanding how to evaluate those databases.

The goal is that the data is all in one place (a single file) that will make backup and portability easier. For small volume usage, pretty much any solution will hold for a while, but my goal is to think ahead and make sure its able to withstand heavy large volume usage as well. Another consideration is also the interoperability with .NET and stability of such code to avoid errors and memory leaks.

How should I evaluate my database options for this scenario?