You might have one component that's causing the trouble. Sicne this board has onboard video, I would remove every component and connection except for:
CPU/HSF
Memory
Powerswitch
Set the onboard video active, and with only these components attached, see if it'll fire up. If it does, put the HDD back on and see if you can boot with it.
If not, then most likely there is a BIOS problem, and if you can't get to flashing it then your board may be toast.
If thats the case, you may wish to look for a replacement...and if it does come to that, I might recommend the Shuttle MK20N...same chipset, onboard video, and onboard sound and NIC. I've got one running a Duron800 and its never hung on me once.
(No AGP though...not sure if the A7V-VM had AGP...)
Mike