Q:

How can I change the installation directory to drive A?

My friend is trying to install Diablo 3 in his windows 7. But he kind of messed up a little with his partitions.
All his files (and also extra space) are in the drive A, but his OS (windows 7) is running from drive C
Every time he tries to install Diablo, he change to drive A but it says "invalid directory" and doesn't save anything there, but instead, it suggest the drive C (where there is no space left).
Could it be because A is originally for Floppy disk? How could he fix it?

A:

My guess is that the installer is based off of some ancient technology developed in Blizzard's dark ages and, as you suspected, you cannot install on either a drive lettered A or B.  As noted, this is because these were the floppy or other external media drives from a long time ago, and it simply won't recognize them as a valid install location.
You must change the drive letter to something NOT A-C (D is always a wonderful choice) in order to install Diablo III and commence the looting.

