Re-install not working again

[NATHAN]

Hi ,ok once again i have had 2 format and now when i re-install hoster it says i have already installed 2 copies. I read in here somewhere before i think that this problem is actually caused by xp changeing its cd code after you have put your code in ,maybe someone can tell me if this is correct. Also can you please reset 1 of my reg's please so i can re-install on my home pc. My laptop is fine as i never have had to format it as yet.

many thanks nath.