an Out of Memory Error occurs when a 32 bit program uses more than 2. 5GB of ram. under default configurations it is not an error that gets thrown for running out of ram system wide. windows will unload processes and shove things into the page file which it has authority to expand as needed.
I'll repeat that 2. 5GB is a hard limit on the process. The bigger question is why is he getting a memory leak. my guess that system has bad data, a run away calculation or far far to many orbital bodies generated.