I reinstalled Windows XP and cannot locate 30GB disk space

["CJ"]

I reinstalled windows XP on my compaq presario notebook computer. I
probably clicked some button to partition C: drive, during the process.
I only used one Windows XP CD, and did not use other manufacturer's
System Recovery CDs.

After the installation, I find my computer only shows 10 GB C drive.
The computer shall have 40 GB disk space in total. I cannot locate the
other 30 GB space.

Please help.