A recent Gartner report on the total cost of ownership (TCO) for Vista stated, “The best way to reduce PC TCO is to improve the way PCs are managed. Our model shows that a typically managed desktop can reduce TCO by more than 13%. Removing administrator access from appropriate users and adding policy and process to consistently manage desktops can reduce TCO by 37% compared with an unmanaged desktop.”

If you are running standalone PCs, and not using group policy and other Directory based features to create consistency among your organization's desktops, your organization falls into the "unmanaged" category. 

Gartner's findings are very consistent with our clients' - that thin clients, especially diskless thin clients that have nothing onboard to manage, reduce TCO by at least 50%.