I got error "The request filtering module is configured to deny a request that exceeds the request content length" at IIS 7.

SUMMARY

This problem occurs because by default in IIS 7 enabled requestFiltering that have MaxAllowedContentLength property. It specifies, in bytes, the maximum length of content in a request. The default is 30000000 (approximately 30 megabytes.)

SOLUTION

To change this value you must include following code in your Web.config file if you want to apply this setting only to you application. If you want to change this setting for all of the computer and not just this ASP.NET application, you must modify the Machine.config file. By default, the element is set to the following parameters in the Machine.config file: The Machine.config file is located in the \System Root\Microsoft.NET\Framework\Version Number\CONFIG directory.

<configuration> <system.webServer> <security> <requestFiltering> <requestLimits maxAllowedContentLength="100000000"/> </requestFiltering> </security> </system.webServer> </configuration>

If you have error that requestFiltering cannot be overriden you must edit mashine.config file and change string
<section name="requestFiltering" overrideModeDefault="Deny" />
to <section name="requestFiltering" overrideModeDefault="Allow" />

MORE

Note During the upload process of large files, built-in ASP.NET loads the whole file in memory before the user can save the file to the disk. Therefore, the process may recycle because of the memoryLimit attribute of the processModel tag in the Machine.config file. More info you can find in Microsoft KB article: http://support.microsoft.com/default.aspx?scid=kb;EN-US;295626

PowUpload ASP.NET control handles and stores the contents of the POST request to a file on the server hard disk rather than loading it into memory as the built-in ASP.NET upload support does. So you willn't have problems with memory use while uploading large files.

REFERENCES

Microsoft Developer Network:
http://msdn2.microsoft.com/en-us/library/ms689462.aspx