I have a new MSI P4M900M3-L Motherboard with 390watts ACBEL True power supply.

I attached to a 17" Philip 170s lcd screen, when I turn on the cpu, the lcd just show "no video output"....

I waited for about 10 mins and the the xp desktop just appear!

So what could be wrong?

Does the motherboard have on board video and are you using a add on video card using the PCI, PCI-E, Or AGP slot? If you computer has on board video and you are using an add on you need to disable the on board video in the bios so the computer will start with the other card. Or at least select to start with the other card.

It is running on the intergrated video.

Check the monitor connection and make sure it's secure

Yes, as tighten as i can....

But as long as i dun shut down its ok. Everytime shut down will takes about 10mins to start..... Could it be the motherboard cannot boot to 17" LCD?

The only way to tell for sure is to try another known good monitor or a plug-in video card. I'd try to borrow a monitor first

i tried on another 17" lcd still cannot, have to find a crt monitor to try.

LCD, CRT, it shouldn't matter. Especially since it's a new motherboard. I'd return it

Have you installed the proper drivers for the integrated video card? If not, does that help the problem?
Rarely (IME) a monitor will also require drivers - have you installed any drivers for the monitor?

I returned the motherboard, they tested infront of me and it just boot smoothly.... Its driving me crazy....

Before you reinstall it, put it on a piece of cardboard on the table and run it out of the case. When you remount the boardmake sure the stand-offs on in the proper place and the solder traces on the bottom of the board are not touching anything. Try another monitor cable