Have your friend wipe your drive clean with a live CD and the qtparted or fdisk utility on it.
Ok so a while ago I had a perfectly good working Windows XP. Then it crash (I don't know why). My friend whp fixes computers had a copy of linux so he downloaded that onto my computer. Later he found a free version of Windows XP and put that on as well. My other friend gave me a copy of Windows XP and now what I would like to do is get rid of linux and Windows XP(the free version) and download Windows XP as my opperating system. I have a disc for Windows XP and if I put that in it says it will download XP for me, but I don't know if it will get rid of the free version and linux. I assume it won't so I need to know how to get rid of all of my opperating systems and install Windows XP. Hope that wasn't to much. If you have any suggestions let me know.