Could you just check for the existence of "C:\"? How many OS's start with a letter, specifically the thrid letter in the alphabet (this is a real question)?

Cheers,

John

Update:

Apparrently you get '--'ed around here for asking what can be preceived as stupid questions. From this and BUU's comments I'll take the answer to my first question as no.

Update 2:

I was talking about the second question at work today with a friend. He said that OS/2 and one of the mainframe operating systems also used letters to denote drives.