you can try the repair option, i cant remember if its there when you press f8 as its starting up, but i know its there if you boot from a xp cd.
personally, i would remove the hard disk, fit it into an external caddy and plug it in a friends pc e.t.c and copy your data across, then format your drive and re-install windows from the cd.
personally, i would remove the hard disk, fit it into an external caddy and plug it in a friends pc e.t.c and copy your data across, then format your drive and re-install windows from the cd.