You can install an FTP server on your web server. This will allow you to access your files via FTP and give access to Dropmysite to back up your files.
Please visit the link based on the OS on which your server is running to get the instructions.
Windows Server 2003 - http://support.microsoft.com/kb/323384
Windows Server 2008 - http://technet.microsoft.com/en-us/library/cc771012(v=ws.10).aspx
Ubuntu - https://help.ubuntu.com/10.04/serverguide/ftp-server.html
CentOS and Linux - http://www.cyberciti.biz/faq/rhel-centos-linux-install-ftp-server/
Solaris - http://en.wikibooks.org/wiki/Solaris/Solaris_FTP_Server_Setup
Dropmysites's Support team is here to help from 9:00 AM to 7:00 PM SGT, Monday through Friday.
Email support@dropmysite.com and we'd be glad to help with all your questions