This is really hard to say since the laptop specs are not complete or available for most people that post on this forum.
Could you describe where you are at right now for confirmation? From what I can gather the installation completed but the system is slow and laggy now, is that correct?
Without being 100% sure on the processor that would seem to be a very old processor that would not keep up very well with windows 7. If your processor is truly an AMD Athlon 64 you might want to stay at XP, although there are some tricks to get Windows 7 to work in a minimum mode it will never be lag free compared to windows xp. Also if the laptop is old enough to include an Athlon 64 most likely you will not be able to get the video driver
, so that would cause a lot of graphical lag.
If you would like to verify that your computer is able to work with windows 7 you might want to download this MS tool
. (this tools runs inside a windows environment)