Quote from ItchyFlea
If you happen to have the old launcher, you could create a .bat file to force the game to use an alternate folder.
Just have the .bat file contain something like this:
"C:\Program Files\Java\jre6\bin\java.exe" -Xmx1024M -Xms1024M -cp "C:\Documents and Settings\USERNAME\Desktop\MineCraft\Minecraft.jar" net.minecraft.LauncherFrame
Thanks, I used to have a system similar to that. I would prefer to use the new launcher if possible though, I have a few mod configurations and I can't imagine the fix being too difficult.