how to uninstall

This requires some more information: i.e is your saystem double booted, what linux are you using etc. If you have genuine windows double boot, just go insert the XP install CD and boot into recovery console and use fixmbr command. Of course there are other methods and I recommend this webpage- www.users.bigpond.net.au/hermanzone/p18.htm. That said and done, why do you want to u7ni9nstall Linux? I strongly recommend you do not do so. Se4arch for other options.