Lenovo M55 8808 shuts down feature selected

[Rapidrob]

I fixed the overheating problem, I then changed the OS to Lubutu,since this computer is so old and has so little memory.
Now I have a new problem. After I boot the computer and select any of the programs options, the unit shuts down and re-boots instantly.
It is not a heat issue as the computer has only been on for two minutes. The CPU/GPU are under 100 degrees F.
This does this even if the on/off switch is disconnected. The memory passed a one hour stress test before the new OS. Power supply is brand new. All SATA cables are new and tight. Hard drive has been wiped,partitioned and loaded the OS via the on board DVD with no issues.
I have not upgraded the BIOS to 2009 versions. Is this a Bios problem?