The value of Diskpart "Clean" command for install failures is to wipe the boot sector of possibly corrupt or conflicting code blocking install. It isn't necessary to run "Clean all" which is more for overwriting data securely and does no more than "Clean" for this critical boot sector purpose.
"Clean" will destroy everything on the HD so that it is recoverable only by Data REcovery software, "Clean all" not even that.
Where did you get Windows 7? You said you've tried two disks - what is their source?
Try writing a verified ISO to flash stick using Universal USB Installer
with Windows 7 in dropdown, boot under USB, Removable or HD's in one-time BIOS Boot Menu.
I would find a HD which can afford to be wiped and try "Clean" command with your 64 bit install problem.
If these fail we can continue troubleshooting your issue here.