SBS and the 3GB switch
For several years, there has been an on going discussion on whether or not to enable the /3GB switch in the boot.ini file for an SBS server. By and far, the consensus of opinion has been to NOT use the /3GB option - especially considering that WSS 2.0 or later versions do not support the /3GB switch.
And, finally, this KB article includes a lot of additional information on the /3GB issue (with thanks to SG for the reminder!):