What is the exact error message that you receive when booting from the iso ? if you could attach a screen, that would be better. what is the exact model of your HD ? is it SSD ? what you could first try is to switch from AHCI or sata to IDE, if this option is available in your bios, that would probably fix this issue and your HD should now appear at the partition window when booting from iso. If the option is not available , you will have to find the right sata drivers for your storage controller and either integrate them to the iso or just put them in USB then load them when accessing to the disk page (partition window).
Sounds like the disk is formatted GPT since it came with Win 8 and Win 7 must have an MBR formatted disk.
No, you can install win7 on GPT disk through UEFI with csm enabled as well. That's not the problem. From what he mentionned in first post, everything suggests that his problem is related to missing sata drivers, that's why his HD does not appear at disk window so he needs to find the correct sata drivers of his storage contoller to get his HD recognized to be able to install win7 unless he switchs from sata to IDE in the bios if this option is available. If so, that should fix the issue.