pc restart automatically after shut down

[Pete]

Hi,

I'm running WinXP on my pc and lately after I shut it
down, it starts up automatically sometimes in 10 minutes
and sometimes shorter. I have to power it off to make it
stop. It doesn't seem like it's in standby mode because
the power is off, at least the light is. I have not
changed any configuration so I am not sure what went
wrong. I have tried uninstalling all the software I've
installed but it doesn't help. I'd appreciate if anyone
can give me recommendations / suggestions to fix it.

Thanks in advance.