I used the disk utility to repartition my main drive, formatted the new one as NTSF, and used Boot Camp to load Windows 7. I fiddled quite a lot with Win7 and finally got it looking and acting the way I want it to. When I get back to Mac OS X (10.9.3 3.4 GHz Core i7, 12 GB 1333 DDR3, 256G solid state drive, split nearly in half for OSX+Win, a 1T ordinary drive for data, and a 3T external drive for Time Machine backups), however, I get an error message pop-up: The disk you inserted was not readable by this computer. [Ignore / Eject] If I select Eject, it comes right back again. If I select Ignore, it's gone until I get back into Mac OS X again - very annoying. I opened up a Finder and noticed that there is a new "Win" drive that has "shared" data between the two operating system environments (a very cool surprise). But every drive seems quite readable: the folders and files appear to be fine). There are no USB flash drives or CDs involved. How can I convince this message to go away for good? Thanks!