Why is backup software trying to access my empty A: drive?

It is not just the noise of the access but I am worried it will wear it out trying to access it 3 or 4 times a minute.  Does anybody have an answer?

Have you tried contacting WD’s Technical Support? I would consider giving them a call about this.

To Contact WD for Technical Support
http://support.wdc.com/contact/index.asp?lang=en