The laptop currently has a 40GB Hitachi Travelstar Hard drive. Its model number is : HTS541040G9SA00. From googling around it seems like the Height is 9.5mm.
In which case I am going to go ahead and buy a hard drive with a 9.5mm height for it.
I'm glad I took some time out and looked into it. They dont even advertise the heights of laptop hard drives clearly sometimes not all even.