Finding computer's name?

Hello,
Hi there, is it possible to get the exact location of a computer using its ip address? (i.e., the computer which is not in the local network) but connected to internet.

And also having doubt about uninstalling ubuntu, My system is not a dual boot. I've installed ubuntu in it. But now i would like to install win xp again. but i'm not able to uninstall ubuntu. could anyone help me in this? i need a clear step-step procedure, since i'm not well versed in networking and computer installing.