I've used Microsoft SQL 2005 Express edition for smaller applications like this. MS Visual Developer 2008 and MS Visual Web Developer make it pretty easy to make data entry forms. I already had a running exchange server that was running Internet Information Services (Microsoft Web Server). It makes it pretty easy to turn on web security and force users to authenticate and log in to use the form. I also caputure their user name and write it to the database when they make an entry.

If you need help or want someone to take a look at what you have to offer a more informed answer I'd be happy to. I do consulting work regularly. Message me if interested.