Got my hands on one of the CASSt-offs from Marc and started putting together the bits I'll need to do a build.
Specs of machines:
CPU: AOpen 2.0GHz Athlon XP+ 2400 socket A (462)
RAM: 1x512 PC2100 (DDR 133)
HDD: Maxtor 6E030L0 30GB
Graphics: NVidia GeForce2 MX400 (64MB)
Audio: onboard Realtek Avance ALC650 AC97 (uses Via South Bridge chipset - KT400 VT8377)
Mobo: AOpen AK77-8XN with a Phoenix BIOS
NIC: onboard Realtek RTL8139 Family PCI Fast Ethernet NIC
OS: Windows XP
CD burner (generic JustLink 52x24x52x)

This makes them better than what we have by quite a bit, but they aren't quite as good as I thought. The biggest benefit is that we now have XP in the labs.

I grabbed a newer set of drivers from the AOpen site as well as an app called SilentTek (also from AOpen) that purports to keep the machine running quiet and cool, but it uses 8MB of memory. Also grabbed the manuals - stored on my machine.

UPDATE: the machines do not have DVD readers in them. To add a DVD drive from existing lab machines will take approximately 30 minutes (5-10 for removing the DVD drive from the current lab machine and 20-25 minutes to install it in the new machine. Problem is that the new machine has a cage that needs to be literally cut apart to insert the extra drive). Option here is to replace the existing CD-RW drive with a DVD read-only drive - is this something we want to entertain?.