a department needs to upgrade its applications, can easily outweigh these. Especially if users object and try to subvert the discipline of waiting for a regular boot turn to upgrade all machines at once. If each user is allowed to do this on their own, then, the discipline soon degrades into effectively a bunch of home computer whose issues are not really diagnosable nor comparable to each other. In which situation thin clients may become the only practical answer: Many organizations use thin clients for applications which require high security, involve unreliable users or repurpose older machines for continued use. This much simplifies boot image control by facilitating centralized management of computers, and has many advantages: since servers manage clients and the local environment is highly restricted (and often stateless), providing protection from malware, support costs are reduced since no application data typically resides on the thin client (it is entirely rendered), it is securely stored on network drives upon its creation since disk, application memory, and processors are minimal in thin client hardware, they go obsolete slowly and cost much less since they are not as useful as ordinary computers they are of less interest to thieves While control of the images is simpler, there are disadvantages. Thin clients: require more network bandwidth require more host computer power and must typically be served by much larger host boxes typically cannot run arbitrary Windows, Linux or Mac software perform poorly in multimedia applications or games - an advantage in many business environments Many organizations try to gain the advantages of thin clients without the disadvantages by treating many very standard machines as if they were terminals, but with very much greater capabilities. As they buy new computers, they put the demanding applications on those. Boot turns and re-imaging Administrators perform a regular (often bi-annual) boot turn that re-images many older, off-spec machines at once so that new hardware can be deployed for higher-end use. This procedure is called cascading: the oldest hardware is repurposed with simpler software to let it continue in use for some less demanding or more access-controlled applications, but subjects it to much more rigorous control to minimize the number of images. The total cost of operations correlates strongly to the total number of different images, not the total number of computers. To minimize the number of images requires additional discipline: Specify the computer hardware to minimize