Default is 768MB based on your RAM capacity. However large your reserve
size is for the pagefile, windows determines how much it will actually use.
This is a result of how much RAM your applications and XP use. And, if
you're switching open multiple applications in the meantime.
There are exceptions like imaging (partition) applications that run as a
service, instead of an open user application. These may beat up the
swapfile.
Dave