PXE failure, alway enter rescue mode

[Cheng Cheng]

Hi all, 

I want to use PXE to boot GRUB. And I already have grub1.99rc1 on my computer.

The command I used to produce the pxe image is:
    grub-mkimage --fromat=i386-pc-pxe --prefix='(pxe)/boot/grub' 
--output=pxe.boot pxe pxecmd

But every time, I can only enter rescue mode. The error shows "file not found"

I think this is because the prefix has some problem, and grub cannot resolve 
the path on tftp.

Can anyone tell me how to correctly set the prefix? I would really appreciate 
it.

Cheng