O.k. to start, I'd say the hard drive was fried! Bummer!! Or the registry was so screwed up that it ain't going anywhere until you get that mess sorted out.
But, try this... If you can access MS via another computer, download and set up their emergency booster files [my terminology]...from... How to obtain Windows XP Setup boot disks
...you will need 6 floppies. It is a simple setup. You will get all the instructions at this URL.
BTW, if you buy another laptop, my suggestion is to never be WITHOUT a floppy port, or an a:\ drive, for just this purpose. Often you will find mfr's not providing one, and hoping that you will use a pre-burned CD to save your skin, but that is for their convenience not yours. Most nutter-computer users, want access to DOS, and the only way to safely do that is via the a:\ and a floppy disk, as far as I am concerned.
Anyway, getting back to this download stuff...if you run the re-setup via these disks and it is successful, then you will know that the unit still has some life in it. And then you can get on with correcting the next problem.
If it is as old as you intimate, how is it that you are running XP on it...and no CD drive? ...or am I mis-understanding something...you say it "only has floppy..."