yep, there are three options - custom size, system managed, no pagefile.
in any case it would be important for an audio machine to have the values for initial and maximum set to the same number, otherwise the system might decide somewhen to increase the pagefile.
for computers with 2 GB RAM or more i don't know for what to use the pagefile (except slowing down the computer), so most of the time i'm setting this to *don't use*, but there are certain configurations which do not like such a setting (eg. photoshop is always moaning about it).
preloaded samples cannot be moved to the pagefile (for obvious reasons) and the remaining 1 GB kernel space should be plenty enough for windows and everything else needed to run from this memory space.
in case your setup does not like the *don't use* setting, what can happen, i'd say select 1024 MB, which is then the same as available kernel space.
christian