As far as I understand, your system hangs on an E7 POST code. If so, to begin troubleshoting, I'd recommend the following:
Restart the system into BIOS. Once in the BIOS setup utility, press <F9> to restore BIOS default settings. Reset any customized BIOS settings. Clear all DMI event logs by setting the option to "Enable", which is located in the Advanced/Event Log Configuration section of the BIOS Setup utility. Press <F10> to save the new settings and reboot the system.
If the problem continues, try BIOS Recovery, as you indicated. The ste-by-step instructions on how to do this are found here:
Note: The .bio file needed for that is posted here: