Occasionally I see numbers like this and I can't figure out what you're doing. I worked in a Windows shop where we had 1200 workstations, about 50 servers, spread over 12 sites. Support for daily problems and a rather complicated inhouse business app was handled by two techs, one DBA who admitted he only put in a good 4 hours a day, and two people to answer the phone and do training classes. These folks were never busy and the only time I ever saw them work overtime was if we were swapping out a server and it had to be done at off hours.
If you're not buying Joe's backroom PCs, hardware failures aren't really that frequent, there are tools that will push security and software updates to workstations automatically, WTS and other tools will let you remotely admin servers and workstations, and if you've got a virus scanner installed (client and/or mail server), you're okay there. Apply a little security to your users (don't make them an Admin) so they can't just install every piece of junk software they think looks neat and you'll reduce a ton of calls right there.
Ghost is a wonderful tool too, make the users save all documents to network drive (which of course is backed up). If they do manage to trash a machine (never seen it happen to anyone who wasn't an Admin), reblast the standard image and boom you're up and running in a matter of minutes. If they are on a portable, partition the drive so that there is a system and data drive. Change my documents to point to the data drive and again if they trash the system, blast an image to the system drive.