Thanks! On the USB flash drive question: The DC-125, since it’s graphics+audio+2 free ports and powered off the USB bus itself, has only enough free ports and power for USB keyboard and mouse. To support a USB flash drive at each station, you’ll want a powered hub and more free ports, and that is what separates our higher end product http://plugable.com/products/ut-1/ from the DC-125. You might want to look there.
Note with the higher end-product, it also supports larger monitors (1920x1080), but on large monitors, for performance reasons you’ll still want to manually set the monitor resolution of each station lower, to avoid the USB 2.0 bus bottleneck as you’re scaling to many stations.
By the way here’s a good video showing WMS 2011’s two different modes for USB flash drives (plug into USB terminal, it’s private to user; plug in to USB root hub on machine, it’s public to all users): https://www.youtube.com/watch?v=R5RQ4i…
For the unused USB sockets on the motherboard, it’s hard to tell – the key is if they’re on their own host controller. I’m not certain, but I think the Intel chipset used in the box you’re looking at has two separate EHCI (USB 2.0) host controllers, so it’s a matter of figuring out which physical ports are mapped to which. But assuming that they made use of both host controllers for your existing available ports, you shouldn’t need to muck with the motherboard - you’d just want to split all your USB terminals so that about half eventually route to one host controller, half to the other. You can get the current picture of what’s happening on your system via. Windows Device Manager’s “View by Connection”.
(Here the two host controllers on my laptop are visible, with only the built-in webcam on the second one).
Note: I haven’t done any testing to confirm performance benefits of spreading across host controllers on Intel chipsets (I’m not sure if internally they share resources, such that they’re not fully independent internally).
In terms of graphics card, the best for USB graphics are actually built-in Intel graphics on the chipset (here’s some background on why http://plugable.com/2010/08/21/whats-…)
For your case where Intel UMA graphics don’t appear to be an option, the next best is a compatible card with a good ability to read data back, since that’s what happens for all graphics that ultimately goes over USB (16x PCIe; card designed for GPGPU work, which is another scenario requiring data on VRAM to be accessed quickly). I don’t like fans because of reliability issues. So if pressed for a recommendation, this one is passively cooled, although I haven’t tested it and the heat sinks may cause it to span two slots: http://www.amazon.com/PCI-Express-EN2… ($44.95)
Last note: To see the full performance of the hardware, you’ll also want to trial Userful Multiseat Linux (free trial available at http://userful.com/) alongside WMS. Userful is much snappier than Windows Multipoint Server, even with one or two terminals, and also shows more clearly what the hardware is capable of (in terms of how many terminals one machine can scale to). Comparing the two will help highlight where the real bottlenecks are.
Again, thanks for the questions and hope that helps!