PC keeps shutting down when putting in CPU

[Disrafil]

I have a Zotac MCP73 mobo that works well with Celeron 430 (800 fsb) but when I put in a core2duo e8400 (1333 fsb) the computer boots up, gets to the os login screen, then promptly shuts down. The specs for the MCP73 motherboard says this motherboard series is compatible with 1333 fsb, except for one version.

 

[CountMike]

You may need a BIOS update.