Vista is a resource-hog and got UAC, thus it is NOT recommended as OS when you host ANY kind of server.
Windows 2003 is more or less the same as Windows XP, except that it got more administrative features, and has had many resource-hogging functions disabled.
So yes, in essence Windows 2003 works with OTserv, in fact it is more recommended to use 2003 than XP since its literally MADE for server hosting.