i have 2 computers 1 i never use any more and that 1 has my registered copy of windows xp on it i have this new pc but it wont let me register my windows xp cd to this new pc is there away to cancel it from the old pc and move it to this pc??? i would use the old hard drive but my new pc uses sata any ideas? i contacted microsoft like 3months ago there waste of time if you ask me 
windows xp registration help
If it's an OEM license (eg. the Windows software came with a new PC when you bought it) then you probably won't be able to transfer to a new PC - this will be against the EULA. However, if you purchased the copy of Windows separately (eg. it's a full retail version) then you should be able to transfer it to a new PC provided you remove it from the old one. If this isn't working, you would need to contact Microsoft directly for help - they usually provide a free-phone number for product activation support.
Exactly like Animal said, use the activate by telephone option. Although you will only be able to activate it on one pc or the other, not both at the same time.
did u mean Windows Genuine or like that? If like that use RemoveWGA
