How to remove xp from dual boot, xp & windows7

i am using dual boot-able operating system windows xp and w7, after trying w7 I've found it so interesting and decided to keep working with it, i would like to remove xp and just keep w7, every time i switch my PC i get boot choice either earlier version of windows or w7 , i would like to know the best way of removing xp without effecting my system, i have heard many others did and they got some errors

Unless you badly need the space XP is using, it may pay to leave it there for a while longer, in case you need to run an older program that's not compatible with W7.
If you are sure there is nothing you want and wish to proceed, first backup any data files that are on that partition.
Boot in with the W7 dvd, choose custom install, disk tools, format the XP drive or partition, continue the instalation to Run Repair Windows to repair the boot loader.

If you go into the start menu, my computer, C drive(where your operating systems are installed) and find a folder called "windows.old" then that is what is causing it to dual boot, but I think that you should leave it just like the other post said about older programs not being compatible. I can't one of my external hard drives in Windows 7 that I can use in xp and vista, I would keep it, but if you want to remove xp, then that is how to do it if you have that folder, just right click and delete the whole thing.