If you have a server that has a bunch of large files on it, but when people download from it it does not allow resume support... where/how would you change that?
If you're running apache: apache is an http server, not ftp server (although it "appears" to work like an ftp server over the web). Thus it cannot resume downloads: each connection is "new".
I'd recommend using proftpd (if you're on a *nix platform) and serve the files via ftp. Of course, if your users are noobs, getting them to use a ftp proggie probably won't work very well.
Strange question. Most web servers support partial content these days, and I do not recall using HTTP to an Apache server that did not support partial content. Maybe your problem is at the client end. Why not try a downloader like ReGet and see if it opens multiple connections - if so, the server is fine and your client program is the problem.