Agree with above... its not so hard to fix a laptop..... and if it dosent require some physical fixing then its even easier..... just formatting and stuff..
Anyway if you have only 10GB now out of 20 then that moron probably partitioned half of it and forgot to define the other 10GB as another drive..... [windows XP dose it automatically but dunno if 2000 does it aswell]
Try to get Magic Partition of some version and see if you can get to partition the other 10GB To another drive........ in order to make one drive as 20GB Again you'll have to delete the whole thing again, bet you don't want this to happen..
Anyway another tip:
ALWAYS Have two drives..... don't have to be 10/10 GB but let yourself have some GB's in the side in order to back-up things incase you must reformat you'r laptop.... to prevent further losses.