Unable to specify the installation media to install SQL server 2008 inside my VM

I have the following:-

1. VM workstation version 9.
2. Inside the VM I have installed windows server 2008 64x.
3. SQL server 2008 ISO image

I did the following:-

1. I have installed the SQL server installation center 64x from an ISO image.
2. But when I click on “new installation” from the instlation center wizard I was prompted to select the installation media, but when I mention the DVd containing the sql server iso image an error message was raised “E: is not a valid installation folder”

So can anyone advice on this , baring in mind the following:-

1. I am installing SQL server 2008 to be used with SharePoint 2013
2. The SQL server ISO image contains three files that ends with; x64 ,x 86 & IA64.

Best Regards