It sounds as if you're doing all the right things. The only other
possibilities I can think of that might prevent the screensaver
from starting are:
1. Some process or application is running in the background which
is preventing the machine from being idle for the amount of time
that you've set for the screensaver to start. You might want to
start troubleshooting this by running msconfig and unchecking all
the startup programs. See if the screensaver starts. Add the
programs back one at a time and see if one of them stops the
screensaver from starting. I'd suspect programs that have an
autoupdate feature such as most antivirus apps.
2. Outdated video or monitor drivers. Make sure you're using the
latest drivers. Long shot, but you never know. Usually they cause
problems with a PC going into standby.
3. Network activity. Disable the network connection and see what
happens. Another long shot for the same reasons.
As far as contacting Microsoft, here are the only options that
I'm aware of:
http://www.support.microsoft.com/oas/default.aspx?ln=en-us&x=14&y=8&c1=509&prid=3518&gprid=185522
Keep in mind that if Windows came preinstalled on these machines,
they're going to refer you to the manufacturer for support.
Here are a couple of other articles that you may find useful.
http://tinyurl.com/4erpd
http://support.microsoft.com/default.aspx?scid=kb;en-us;326719
Sorry I couldn't be more helpful.