When people are trying to help please listen, not just repost the same thing!

The first point is to establish if the connection issue is with your usb on WinXP to the N900. To do this you must follow the instructions and connect in Mass Storage Mode. IF this works then you can proceed to check if the PC Suite Mode works. If it doesn't then you have more complex issues that need fixing first.

To use PC Suite mode you must have installed and configured PC Suite to use the USB cable. Make sure you are not using OVI Suite as this does not appear to work properly with the N900.

If you are still having issues then post exactly what you are doing and the results.