checksum error Defaults Loading

Got a Emachine Vista Home
checksum error Defaults Loading was the message I got
Changed the battery over and still the same
The strange thing about this is no matter what I go into
f8 f2 f1
It shuts down but there is no errors or beeps or blue screen
I timed it and the pc stays on for 2m 30s and then dies
I'm totally baffled with it

Most likely overheating,
Unplug from the wall and open the case.
Clean it out. Check to see if all fans move easily (without plugging in).

Plug in (with case open) and run until it shuts down.
Unplug from wall
CAREFULLY feel around near the components (DO NOT touch them - you can burn yourself!) to locate the hot components (don't forget to check the PSU)

It's gotta stay on longer than a couple of minutes in order to run diagnostics .
For the checksum error, go into the BIOS, set the date, then save the settings before you exit. Does it still give the checksum error the next time that you reboot?