You would have to tell us (or post a screenprint at some image hosting site) what disk management says exactly.
7.48 GB on the c:-drive for XP certainly is unworkable and it will become worse with each Windows update. So either you have to merge partitions or (better) replace the drive. You can clone the contents of the current c:-drive to it, so you wouldn't have to lose anything.
That your father has the same netbook but with a bigger hard disk only means it's not the same configuration.