Boot Problem - Biostar U-8668D V7.2 MBoard / P4 1.8GHz

Symptoms of problem :
1) Power-up using the casing's on/off switch. I will get the system run thru the BIOS test and POST. The it comes to Windows XP's logo and a rolling bar rolling down there and it will roll forever and the system just halted like that. I have to press and hold on to the on/off switch for 4-5 secs to power down.
2) then i power-up the system again using on/off switch. this time after all the POST, it go to "SAFE MODE" option screen where I will choose "Boot Normally" ... and it boot up the windows perfectly.
3) and when in the perfect running Windows mode and i choose to "Restart" the PC, it boot up again after shutdown perfectly.
4) but whtn in the perfect running Windows mode and i choose to "Shutdown" the PC, and have to switch in the on/off switch again to power-up the system, the problem similar to (1) happen again.