AspMaxRequestEntityAllowed
I received a mail from somebody saying that he was having an ASP app that uses VB6 component to upload files to a server. He has recently migrated to IIS6 and now if he tries to upload a file bigger than ~300k it returns an unspecified error.
I just recalled: AspMaxRequestEntityAllowed. The AspMaxRequestEntityAllowed property specifies the maximum number of bytes allowed in the entity body of an ASP request. If a Content-Length header is present and specifies an amount of data greater than the value of AspMaxRequestEntityAllowed, IIS returns a 403 error response. This property is related in function to MaxRequestEntityAllowed, but is specific to ASP request. Whereas you might set the MaxRequestEntityAllowed property to 1 MB at the general World Wide Web Publishing Service (WWW Service) level, you may choose to set AspMaxRequestEntityAllowed to a lower value, if you know that your specific ASP applications handle a smaller amount of data.
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/iissdk/iis/ref_mb_aspmaxrequestentityallowed.asp