Crystal Reports: Access to report file denied. Another program may be using it.

In crystal report when you got an error: Error in File (report name).rpt:
Access to report file denied. Another program may be using it.

The following image shows the error page

Solution: Give IIS_IUSRS user group write permissions to the folder C:\Windows\Temp.

If you have multiple virtual machines (servers) that connect to a shared folder of code in another virtual machine or server, you should give permissions to IIS_USER on every server, not only the hosting server.