Silverlight is VERY light. It runs in a browser. Memory requirements wouldn't be much more than what the browser requires.

>Can you share why (the reasons) your client is looking at Silverlight? Is this a database application or much more? I would be curious to know the minimum memory and OS requirements necessary to run an average size (about 30-40 windows) database application developed in WPF and/or Silverlight?
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>My concern of rewriting a VFP application to WPF is not only it will be a gargantuan development task but the customer would have to upgrade the entire hardware to run it.