This setting in your web.config file is able to be updated to control this.
<httpruntime maxrequestlength="1000000" executiontimeout="9999999">
Remember to save your changes for the settings to be applied...
It seems that IIS7 now has a different parameter for this setting, and it's in bytes rather than KB. "In IIS7, you specify the maximum size of a file to be uploaded to the website by using the maxAllowedContentLength setting (system.webServer/security/requestFiltering/requestLimits >> maxAllowedContentLength)." For example, you can try something like this in your web.config:
<requestLimits maxAllowedContentLength="1000000000" ></requestLimits>