40 GB space lost from HDD

[raksrules]

My roomie has a Dell studio 15 laptop which has 320GB Hdd space. he had used some tool to partition it. Something went wrong and his laptop shutdown. Now the problem is that the computer management shows 40GB of free space without any drive letter assigned. i tried to assign a drive letter but in that wizard at end shows "there is not enough disk space to complete this operation"
How do we reclaim the 40GB

 

[Gaurish]

Reparition the whole HDD again by creating a new partition table. you can you Gparted Live CD for the same - free to use.

GParted -- Screenshots

 

[thetoxicmind]

Repartitioning the HD is the safest option.

 

[sanjeevgpc]

Try some third party partitioners. Looks like boot sector has gone corrupt.