I've had a very similar experience. Going strictly with WinPE 2005 (all legit and properly licensed). Virtual PC 2004 SP1 is pxe booting off a RIS server using the RFGB floppy image, it loads all of the files it needs to boot (effectively this means it passes tftp textmode downloading, gets the binl service reply for which driver to use, downloads dc21x4.sys.. runs right up to loading the ntoskrnl.exe.. then produces the WinXP gui complete with beamers.. 14 shots.. and goes toes up.. it produces a Blue Screen of Death). The error message is rather obscure but documented in the Microsoft Technet as Debug error 0xBB with parameter 0x3 which means [ DHCP IOCTL to TCP failed]. On some Intel boards I've had 7,15,25 minutes an then a successful boot. I'm pretty sure it's driver related. Sure wish we could get a handle on how to fix this.