The size of the model that the program can handle is dictated by the 2 GB paging file size limit in 32 bit operating systems.
When you run the analysis, a number of files are created for storing results - nodal displacements, member end and intermediate section forces, reactions, plate stresses, etc. If you add up the size of all those files, if it exceeds 2 GB, the results cannot be displayed in 32 bit OS.
If you have a large multistorey building with a number of slabs and shear walls, the limit will be reached quickly - around 20000 elements and a 100 load cases.
As rforres1 says, the RAM programs are a better choice for such buildings.