Memory Usage

Hi, trying to find the amount of main memory a running program is using.

I only see commands to find Vid Mem.

What i'm doing is hitting the 'windows' key and having a look at the 'blitzcc.exe' process in the task manager.

Is this a reliable way to find main memory usage?

I'm running on a 512Mb machine and was wondering what size of program I could run on a 256Mb machine.
(under Windows Xp)

Thanks
Marg