Answer
This question was answered on September 7, 1999.
Much of the information contained herein may have changed since posting.
What it sounds like to me is a configuration problem in your CMOS. When you first fire up your computer, it prompts you to press a certain key to enter setup. You have to be pretty quick to see this, so watch carefully and press whatever key it states to press so that you can enter setup. Basically, it appears that in the CMOS is set up backwards: what would normally be a: drive has been established as something other than a 3.5" disk drive, and whatever drive would normally be designated as your cd-rom now occupies some other setting. Make sure in your cmos that the drive letters reflect the proper settings. a: should be your floppy disk, and d: is probably what your cd-rom should be.
You may also have an anti-virus program that is set to scan all drives during access. These programs can cause random accesses of your drives at any time.