This article will attempt to pull the various settings that might restrict uploads into an IIS-based web server into an easy-to-check list.

IIS (6.0 and above) uses HTTP.SYS as the kernel-mode HTTP listener, and frequently runs an application-layer framework like ASP or ASP.Net, as well as ISAPI filters, modules and handlers, all of which can implement different limits, or change request/response behaviours.

If you encounter a limit in a particular component, please add it to this list.

IIS 7.x

HTTP.SYS IIS ASP ASP.Net Probably unrelated unless dealing with thousands of concurrent requests and/or uploads:

IIS 6.0

HTTP.SYS - as above
ASP ASP.Net as above