ignition

Well I posted something yesterday, but I am unable to find it
for some reason, so I am posting my question again. I have
a 2003 chevy malibu. I just put a new battery in it because
the old one died. I was unsure why it died because it was
not that old of a battery.So I connected the new battery and
everything seemed fine until I tried to start it.  Once in the
start position I lost power to the whole vehicle. I
disconnected the battery and I have power again once
reconnected. I can turn the ignition to the on position and
still have power, once i turn it to the start position i lose all
power again.  Do i have a short between the ignition and
the starter or is there some thing else causing this. I
checked the vaultage on the battery to see if it was drained,
and I still had 12.5 vaults at the battery. I checked all the
fuses and the good. Some seemed like the were not as
bright as others. Which I believe is not being enough power
to that area.  Could that be a parasitic draw. Im lost on this
one if you guys can please help. From a learning
technician. Thank you for your time.