i use sccm 2007 R2 for creating images for dell optiplex 990,980, gx 755 gx745.760 etc..we created win 7 image of 990 & 980 thru sccm. these new models of dell 990 980 when network card image fails connecting. we download latest broadcom driver from dell website.
all other system win 7 image starts connecting to network and work succesfully.