Xp Will Not Load

I have a laptop running on XP. When we switch the laptop on, it displays a message "System presence detect unavailable, startup halted" or words to that effect. It then seizes up and I have to turn it off.
It was OK when it was turned off the previous night. Any help at "dummy" level would be appreciated.
Thanks
Keith

Be useful to have the EXACT error message

Can you start it in safe mode?

Welcome to Windrivers Axus.

Have you recently updated this laptop?
What point exactly does it freeze - do you get to the windows loading bit?