Paul is absolutely correct, the fact that your program didn't crash under Windows XP simply means that XP manages memory differently but the bug was always there. I've seen this a million times. So look through the call stack to trace it back to a function/method in your own code that causes the crash. Although judging by your previous post, most certainly you have some sort of a buffer overrun, or use a pointed to a memory block that was previously released. There are a million of possibilities here without seeing the code... I agree with one though -- it is quite a b**ch to deal with if it wasn't caught immediately during development. Good luck.