Free Space in my Laptop

[tzvim]

I use a Lenovo R61i with XP. The Hard Disk is divided to 30G for hard C and 80G for hard D. The Hard disk C is just 10% free. I cannot see what is taking so much because most of my files are in Hard D.
There is any software that I can use and help me to find what I can delete or transfer to Hard D.
Tanks in addvance

 

[iPwn]

WinDirStat

 

[tzvim]

I download this software, how I use it to check the hard disk files