This came up as a solution to a recent issue with files above 30MB being rejected by IIS7.
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IIS7 has a built-in request scanning which imposes an upload file cap which defaults to 30MB. Again, this is a good feature, but it gets in the way if you're looking to upload files larger than 30MB. Steve Schofield posted about how to change this from the comandline:
appcmd set config "My Site/MyApp" -section:requestFiltering -requestLimits.maxAllowedContentLength:104857600 -commitpath:apphost
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from here: http://weblogs.asp.net/jgalloway/archive/2008/01/08/large-file-uploads-in-asp-net.aspx