Moving Files from C Drive to D Drive on Server 2003

When you find the C: drive is full while the D: drive is still empty on your PC, what will you do if you want to free space on C: drive? I am just a home computer user rather than a computer technician, so the first thought on my mind is to move files from C: drive to D: drive. However, it is not as easy as what I think. While trying to move files, I nearly delete some important data due to mistake. When files have been moved to D: drive, I found some programs are unable to be run while the system says that the location of the program doesn’t exist. So I need to move files back to C: drive again, which waste me a lot of time.