As the size of hardrives increase, more people are using partitions to seperate and store groups of files.
Windows XP uses the C: Program Files directory as the default base directory into Which has installed new programs. However, you CAN change the default installation drive and / or directory by using a Registry hack.
Run the registry Editor (regedit) And go to
Look for the value named ProgramFilesDir. by default, this value will be C: Program FileEdit the value to any valid drive or folder and XP will use that new location as the default installation directory for new programs.