Can this be install "over" the existing system or will it erase the existing system.....I am trying to get to my data (see my other post) to back some of it up.....I am not ready to reformat at this point without trying everything I can. My older machines used to reinstall 98 on top of the current operating system and I did not lose my files. Is it the same with XP because when I get to the point of installing it gives me a warning that there is currently an OS blah, blah.