why is sysprep stopping my network card from booting!!!???

I have prepared machines for cloning using sysprep, and prior to intstalling, PXE booting was not a problem. Now that they have been prepped, they wont boot through the pxe server. If i allow them to boot, the installation runs fine, and I can then perform a network boot again. Im presuming that sysprep has done something to my network card settings or disabled it somehow? I have tried prepping with both detect non plug n play devices, and detect plug n play.

Should i remove/disable my network card before prepping and then once prepped try booting?

Hopefully im missing something simple, but any help required as im in a hurry to sort this 🙂

Duncan