It happens because you are using an OEM installation disc. Microsoft has forced the OEM discs to be sold as crippled, so you can ONLY install them from the same install disc to the same hardware, so e.g. discs that come with Dell D620 will work only with Dell D620, not on Dell 930, not on Acer, not on Macs. Even if you get the disc recognized (ISO) it won't do with Easy Install or with any install. If you had non-OEM discs, you could just point to the location to the ISO file / install disc, and it'd be ready to install.
The only way you might be able to get past this was if you installed the OEM Windows on your legal PC hardware, so on the hardware those Windows install discs were sold with. When that Windows install is complete, then download VMware Converter, and convert the Windows to a Workstation VM. Workstation VM will work straight away with Fusion (if you want to have the folder structure to be equal to those created with Fusion, after you have copied the Windows VM you created with Converted to where you want to have it on your Mac, say ~/Documents/Virtual Machines, change the folder name from Whateveryounamedyourvm to Whateveryounamedyourvm.vmwarevm and select hide extension. And it's sorted). Then get rid of the Windows that you have on that original hardware as you technically would have the license to use it on one computer.
OEM discs will behave the same even if tried to install natively, with Boot Camp, Parallels, Fusion, Qemu ... Blame Microsoft and OEMs. The only kind of Windows installation discs that will work will be Full versions of Windows - so not even Upgrade discs.