BOAC I hope you havn't taken my comment on Windows admins and sys admins as a which is the best OS flamer.
In my day I was both.
Windows support staff will without fail either take control of your machine using software and do the changes with you watching or pay you a visit. They can't help themselves and the OS doesn't lend itself to being fixed any otherway.
Any unix sys admin would never leave there seat in thier office, they would just telnet into the machine and edit any of the required files. There are many different ways you can change the resolution.
1. Config file in your X11 xorg.conf if you using X11 drivers
2. Change the users .login file to use the xrandr (don't muck around with this one if you don't know what your doing it can shag your monitor)
3. Or if the user wants to try a few different ones press crt-alt and either plus or minus to flick between supported modes.
4. Use a GUI as has been mentioned
There are a load of otherways as well depending on the flavour of linux/unix.
The problem is when the windows first/second line support think they can also fix unix issues. 9 times out of 10 they turn a 2 min telnet job into a "sod it, it would be quicker reblowing the OS onto this thing than going through the log files to find out what they have edited.
So my post was more a dig at IT support staff fiddling with stuff they haven't a clue about. I always made it very clear where ever I worked that I had zero clue about Apple Macs. I would have never dreamed about having a play with a system and get the hopes up of the user that it was going to be sorted. My limit was printer problems if the toner was full and paper in it and it printed from laptop, if it still din't work after a reboot they were on there own.