True tales from Customer Support: How do you spell "A:"?

I once received a phone call from a customer who needed help getting his computer connected to the Internet. In those days Windows 95 didn't install, by default, the TCP/IP protocol, and thus getting connected was harder then than it is now. The customer in question had been given some floppy disks by his IT department that contained the Windows 95 install files and the ISP's software (Windows didn't ship with a web browser either). This conversation started out poorly and went downhill from there:

Me: Good afternoon, how can I help you?
Customer: I'm trying to get my computer set up on the Internet, can you help me?
Me: Sure, what's the problem?
Customer: The computer is asking me for a disk and I don't know which disk it wants.
Me: What is the message on the screen?
Customer: The computer is asking for Windows 95 Disk 2.
Me: Ok, so insert Windows 95 Disk 2 then.
Customer: The problem is I have two stacks of disks and they each have one labelled "Disk 2".
Me: What do the disks say on their labels?
Customer: Well, one says "Windows 95 Disk 2 of 13", and the other says "Sympatico Install Disk 2 of 4".
Me: ... Ok, well, the computer will usually be specific about which disk it wants, so if it asks for a disk labelled "Windows 95 Disk 2" I'd insert the one from the pile of Windows 95 disks.
Customer: Ok, then what?
Me: Well, you insert the disk and press enter. If for some reason it can't find the disk, it will ask you where it is. Just type "A:" and press enter.
Customer: How do you spell that?
Me: Well.... it's the letter "A", then the colon symbol.
Customer:......
Me: It's next to the 'L'.
Customer: On which side?

I wish I was exaggerating this story.