Extrenal hard drive showing full when its not

[Sam49]

Can someone please help i am running windows XP Pro with an extrenal usb hard drive, i use this extrenal hard drive to store backups of my C: drive made with Norton Ghost. this works very well but now the external hardrive is full so i deleted some of the first backups i made. the problem is that if the file is small enough to go into the recycle bin it is ok and i get the space back, but if it is to big for the recycle bin, the computer asks do you wish to proceed it then deleats the file but does not give me the space back on the hard drive. Even now i have deleated most of the files the hard drive is still showing it is full. anyone know what the problem is please.

[glc]

Open a command prompt and type CHKDSK X: /F (where X is the drive letter).