I run several Library's and when my customers come in to use our computers which are all standard Dell's they want to do homework, resume updates etc. they plug in there USB Flash drive and not all my machines recognize just any USB Flash Drive? Why is that when I though they were all standard? :confused:

A lot depends on the version of Windows the computers are running.
Generally, USB flash drives are have no problems with Windows 2000 and Windows XP.
I don't have experience with Windows Vista.

The comuters may not have updated USB 2.0 drivers, your users flash drives probably use USB 2.0. The USB drivers on your machine may be using USB 1.1 drivers
Make sure you go to windows update on each machine and have everything updated.
If this is not the issue, do you have to machines that are same make and model with same Operating System and a flash drive works on one and not the other?

If this is so there may be a problem with your usb ports

Some things to consider.