The DCS system that I use, and those I know of, give you specific version of Windows, service packs, and hotfixes that you must install. Deviate from that list and if you need support or are trying to get something done because they screwed up or had a bad bug, they'll just tell you that it's not their problem because you did not run the recommended configuration. I have seen a vendor argue over the 4th digit of a bios revision number because they could not find a cause for the bug we reported. And the only way we got away with that in the end was that they had documented a valid upgrade path, coming from an earlier software version, in which case that version was allowed.
My servers run
Windows 2003 because they say I have to
Standard edition because they say I have to
Service pack 2 because they say I have to
And a handful of hotfixes that come with the software installation disks. Because they say I have to.
And I will keep running that particular set up until we upgrade to the next version, when we will switch to windows 2008, standard edition, SP whatever, which some hotfixes.
That is why our network is disconnected from the outside world, all equipment is in locked cabinets, and all computers are in a locked serverroom with kwm going out to the field terminals.