>Is there a way, in an app, I can check to see if there is a disc in A: drive before copying files to it?

I'd highly recommend using the Windows Script Host over any other method, if it's available. It's both simple and not prone to the possibility of Windows throwing an error like DISKSPACE("A:") is under Windows NT. The following snippet determines if the drive is ready.

oFSO = CREATEOBJECT("Scripting.FileSystemObject")
oDrive = oFSO.GetDrive("A:")
? oDrive.IsReady