After some recent odd occurrences on my P3, 500mHz computer, I ran Norton diagnostics test on memory modules. It returned a Fail: Error detected at address 257814528. I rebooted and repeated the test with the same result and address. Third time it came up with address 255651840. Can these addresses help identify which module is at fault and what should my next move be? The Gateway PC came with 128mb to which I added a further 256mb a year ago.