Some other reasons why W7-64 won't boot:
- Boot order reset in BIOS? (spurious)
- SATA/RAID drivers required to talk to the HDD? (and possibly no 64bit drivers available at time of upgrade?)
Most of the other issues mentioned above *shouldn't* cause W7-64 to fail install.
However, it would be nice to see some evidence of the BSOD screen or similar in order to troubleshoot facts.
