right... the small person (aged 7) in the household is wanting a laptop for christmas and frankly that ain't gonna happen!

i had an idea though to get her in front of a pc (that isn't ours) so she can start to do her schoolwork on it (as they are given internet based learning) and play some games etc
i have an old dell 4500s (circa 2002) that seems to work ok... i haven't used it for a couple of years but it has never been problematic and I have just booted it up and it all seems to function ok
what I want to do is wipe it completely, get rid of all the old programs and saved rubbish on there, and then install some very basic windows os (as she uses that at school) that is not cluttered and will function with basically a browser etc and any security software (recommendations welcome) that we can lock the desktop down with so she doesn't get any nasty surprises

its not a world beater when it comes to specs and i think it is carrying about 512mb ram.. used to manage my adobe suite software admirably
http://support.dell.com/support/edocs/SYSTEMS/dim4500s/specs.htm#1101572what might my options be please? cost is an issue so I don't want to be spending out on copies new windows etc.. its currently running xp home edition
would giving it a reformat of some sort be the best option.. i am happy to do this if it clears everything in one hit and gives her a clean pc to muck about with
tia - Guy