All this talk of copying/cutting and pasting... just open the d drive, open another window with your graal folder, right click and drag the graal folder to the d drive, and release right click and select Move Here. Not difficult at all. :P
Also, when you go to download newer versions of Graal, just be sure to change your drive to D instead of C.
Drive letters just assign themselves via which drive it detects first. My one harddrive is also partitioned into 2 drives, so I have C and D as harddrive space, E as CD rom, and F as CD-RW. You could partition your drive to have like a ton of different areas.... You could get an 80gig and partition it 8 times to get 10 seperate drives.
C, D, E, F, G, H, I, J, K, L... lol I forgot what happens when you pass Z, doesn't it start doubling the letters? Like AA BB CC? I have no idea heheh.