It might be useful for the Exchange Server 2003 admins. The Performance Team explained three different ways to find out if the /3GB is enabled, as follows:
We’ve talked a lot about the /3GB switch and its effect on system resources in previous posts. Today we are going to discuss how to determine whether or not /3GB is enabled on a 32-bit system without looking at the boot.ini file or using MSCONFIG.EXE. Finding out this information is not as difficult as you would think – there are actually multiple ways to find this information. We are going to find this information in three different ways – by looking in the registry, by using PSTAT.EXE and by looking at a Memory Dump File. So, without further delay, let’s look at the simplest of the three methods – finding the information in the registry.