Offsite data storage

We need an application for offsite data storage.
The application must run under windows 98 and higher and integrates with windows as if you are using a local hard drive. The data stored on this hard drive should be transferred to a server.
There are some restrictions. The user can only use a restricted amount of space on the server. Also the used bandwidth should be monitored, after a certain amount the bandwidth should be limited to 10kb/s The server is a Suse Linux server. Internally you could use ftp, so standard components can be used. The settings (accounts, limits etc) have to be plain text files or pulled from a mySQL server, so it can be configured by an web application (this webapplication is not part of the job).
Because we're a startup company we need to do this with a small budget.
More info: info@boesmedia.nl