I am sure that I attempted something that I shouldn't have, but I am hoping that there is an easy (and easily understood) way back. <Note: Consider the problem which my ignorance has caused, and tender any any instructions with this profound handicap in mind.> I have a Refurbished Mac mini with OS X Server 2.0GHz quad-core Intel Core i7 <==notice how I have cleverly chosen to cut and paste (that is the level of my technical prowess) that description straight from the invoice that came with it. It has stuff on it, which I may or may not be able to recover from other locations. I also have an old and now completely dead (as in, "destroyed") Acer AspireOne netbook. The netbook ran Windows XP. Having removed the hard drive from the dead shell of a netbook, I plugged it into an adapter and attempted to see if I could use it as an external drive to maintain a few antiquated Windows-dependant programs, after I had already migrated most of the rest of it (i.e. pictures and iTunes) over to the mini. In the course of the afore-mentioned migration, I noticed that one could (if one was not me) choose to have the mini startup, booting from a different disc. "How simple," I told myself. ...and for just a moment it was. Having selected the (now external) drive with XP as my startup drive, all seemed to be going well. ...until I received a message to the effect that an error had been encountered, and Windows had been disabled in order to protect my computer. "Well, no problem," I thought. "After shutting down, I will simply unplug the external drive with XP, and restart my mini using OS X," I continued still unshaken. Unfortunately, the mini still seems to be looking for my unreliable copy of XP, as now I continue to receive a message to the affect that my mini lacks a bootable disc. I am now shaken. ...and humbled ...by my ignorance... ...help... ...please, help.