Slow down.
Something is very wrong here.
The system should be stable, before you waste time installing.
GPT is a kind of partitioning for disks. It is used for high capacity
storage systems, such as huge RAID arrays perhaps. It is the
successor to MBR based partitioning. If you want to use a 3TB
disk and use the whole thing for C: in Windows 7, then GPT is
how you'd do it.
http://en.wikipedia.org/wiki/GUID_Partition_Table
I doubt very much, the disk actually says that. So
something is very wrong here.
*******
If the CMOS battery in the motherboard is bad, *and* you turn
off the power at the back of the PC, then you will lose your
BIOS settings.
If you leave the back of the PC powered, and try reboot after
reboot, the BIOS settings will not change.
It sounds like your BIOS settings are changing while the
power stayed on. This is not good! I don't think I've ever
run into a case, where someone had unstable BIOS settings
while the power remained on. It would take a duff power
supply (out of spec) at the same time as the CMOS battery
was flat, to come even close to doing that. If the motherboard
is Asus, it would take an "Overclocking Failed!" error message
on the screen, to mess up the BIOS settings.
I would turn off the computer and have a snooze. This is
getting too freaky. What kind of malware would do this ?
*******
Are you being entirely honest with me ?
Is there only one hard drive inside this computer ?
Or do you have many disk drives ?
I recommend only having the Windows 7 drive connected
during the installation. That way, nothing
bad can happen to the other drives.
That is what I do, when installing an OS. I pull the
data cables off the other drives. Before I instituted
that policy, I had a few instances where the wrong
drive got blasted. Maybe IT guys don't pull the
excess cables, but *I* do. I hate cleaning up a mess.
The DVD drive should not be disappearing. If I had
to guess, the BIOS is changing the disk controllers
in a way that only enables four of six ports, and the
DVD is on one of the other (disabled) ports. Or something.
I really don't recommend installing, when everything is
shifting underneath you. There really isn't a point to it.
How stable is the machine going to be five minutes
after you're finished ?
*******
In terms of debugging techniques, you're going to need
to simplify the hardware setup, and continue testing,
and try and establish a configuration that isn't changing
all the time. If the motherboard is defective, then
you're going to need to do something about it.
And if the BIOS really is changing between POST attempts,
then critical settings like VDimm or the Northbridge
voltage could be changing. Any number of settings
that change, could make the computer crash prone.
When you change the BIOS settings, you select "Save and Exit"
when you're finished. That stores the settings in CMOS, for
the next POST. If you select "Discard and Exit", none of
your changes will be kept.
Of your two DVD drives, disconnect the data cable of the
one that is disappearing. And see if at least that
annoyance is out of the way. If the remaining DVD is on
an IDE ribbon cable, put it on the end connector (as Master).
If your BIOS setup screen, has a "Hardware Health" tab,
you can check the 3.3V, 5V, and 12V measurements and
see if they are within 5% of the nominal value. In other
words, 12V between 11.4V and 12.6V.
Good luck,
Paul