I'm not sure if SH is designed to take advantage of additional memory address space, but if it is, there is a 'switch' that you can use on the Microsoft support page, you would have to patch your XP 32 bit to SP3 to use it.
It gives an example of how to change the code for use on 'Windows Server 2003' but It does work on XP home/pro editions.
I use it to run 'Trainz 2010' & it sure cut the stutter in that down to near zilch. (link below) scroll down to /3GB.
http://support.microsoft.com/kb/833721