I am unable to install autocad 2011. And in this when I try to install this so at that time I get an error like this C: \ Windows \ system32 \ ntdll.dll. And in order to fix this I have tried many of the solutions but none of them work in my case. So related to this if you have any kind of suggestion then please share this over here. And also in this I have tried to reinstall it again and again and all the time I get the same error so please help me.