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Are you talking about 2 PC's or 1 PC with dual boot (W98 + XP)?
If 1 PC, then you should know that W98 cannot access XP when XP runs with the NTFS filesystem.
If you have 2 PCs connected via a network, then the W98 PC can access XP.
Please take a few minutes and fill out the specs of your PC('s) in your user-profile (just click on "user-cp" at the top of this page).
Then explain in more detail what exactly the problem is.