limit of pivot table

I have a worksheet I set up a pivot table for, it has 500 rows and 14 columns when I try to put 4 items in the pivot table row I get “ Microsoft excel cannot make this change because there are too many row or column items”. In the help file it said the maximum number of items is 8,000 is an item a cell a word or letter? It also said the number of rows and column is limited by memory, I have 64MB of ram but 2 GB on the hard drive, I think windows use the hard drive for memory when the ram is full, is this right? Thanks for any help.