Are there others that can provide a Windows buildbot? It would probably be good to have two -- and a WinXP one would be good.
How much work is it to set one up, and to maintain it? Maybe I can offer an XP VMWare image.
Setting it up essentially requires to put all the software into place, see the wiki. Maintaining it requires attention in case it suddenly hangs, which it does more often on Windows than it does on Unix. In particular, when a process fails to terminate, subsequently it may fail to remove or modify files, and then it breaks completely until the process is killed. A weekly reboot would like fix the majority of the maintenance problems.