computer wont boot and makes wierd sounds

From: Greg (gkornecki_at_msn.com)
Date: 04/19/04 

Date: Mon, 19 Apr 2004 12:26:02 -0700

My friends computer is on the blitz. He says he got a cpu fan not working message that prompted him to shut down.
Since then he's not gotten the message.
When we try to reboot the computer evertything seems normal until about 15 seconds into the boot when a wierd sound starts...a tone that repeats....sort of sounds like a european police siren...long short long short long short...etc
This sound does not always happen.
We can never make it to the xp screen.
We noticed that the case fan is not working and have removed it. The same sound results...let me clarify..the sound does not always occur..but he can never boot up.
The cpu fan itself seems to be spinning fine....as well as the power supply fan.
He has a 1.667 athlon with xp for home.
Any advice?