I don't think you can actually uninstall IE6 from XP, but you can try and repair it.
If you do a reinstall of XP (over itself), you'll keep your data and programs, but you'll need to reinstall all the Windows updates. But no need to reactivate.
You can also try sfc /scannow (Method 1 para 1 of the MS article).
Otherwise, you'll need to modify the registry first, before you can reinstall IE6 (method 2 in article.)