400GB hard drive only showing 38GB

[worthbillions]

I have a 400 g sata which I am using as a secondary drive. When I had a associate try to install win xp professional on it but he messed up the drive. He did n ot load it and so I have only 38 gigs of use. How do I get the 400 gs. back? Thank you.

 

[hughva]

Open disk manager, remove the existing partitions and re-format.