XP/VS Server and ThinClients
As XP/V S Server is fully compatible with Microsoft Terminal Server / Remote Desktop Services any Thin Client which works with those solutions can also be used with XP/VS Server.
So it should offer either rdesktop or FreeRDP as RDP client.
We would recommend using FreeRDP if possible.
Examples:
Wyse C50LE Thin Client which with "Wyse Enhanced SUSE Linux Enterprise"
http://www.wyse.com/products/hardware/thinclients/C50LE/index.asp
HP Thin Clients
http://h10010.www1.hp.com/wwpc/us/en/sm/WF02d/12454-12454-321959.html
Igel
https://www.igel.com/de/produkte/hardware/hardware-uebersicht.html
As far as we know Dell currently does not offer any Thin Clients.