could someone please help me????

[Billy B]

my hp laptop (bought about a year and a half ago) w/ xp
pro keeps suddenly shutting off, and when i push the
power button, it will start, then shut off, and then i
wait a while ( a minute) , and each time, it stays on for
a while longer, then eventually it will stay on for about
half an hour (not quite sure, i haven't timed it)

if i have to read this on site please e-mail me if you
know what to do, or need me to answer some more
questions, thank you

billy,