well it should never freeze in the bios so it looks like it could be heat or board related. Not hdd.
hows the cooling on the unit?
any fan noise?
always used on a flat surface ?
Plenty of airflow underneath?
In the bios area how long before the freeze occurs ?
What Bios version are you running ? this is in the bios area ..... (latest is Version: 1.13 but check - not recommended to run as a freeze during a bios update renders your board useless)
Have you added any 3rd party RAM >?
please do this next :
Remove the hard disk again from the machine and power up into bios without it attached to see if it freezes.
hang in there and we will at least narrow it down
so far we now know its not software (elliminated by bios freeze) hard drive although seen in bios can still stop a boot/freeze up machine so removing it elliminates it from the equation. Heat build up due to the fan being dusty can cause componants to get hot and stop working.
Overheats the board would just turn off the machine and this isnt happeneing so we dont think its an overheat.