There is something about OS X 10.10 Yosemite that causes this driver to fail. The bootcamp partition must be created under Mavericks or the driver will not work. Note: When the driver works it automatically assigns a drive letter to the OS X partition. When it doesn't work it does not assign a drive letter and the option to assign a drive letter in disk management is grayed out. I have tested a number of different combinations trying to get this to work. For my testing I tested Windows 7 Professional x64, Windows 8.1 Pro x64, and Windows 10 Technical Preview x64. They either all worked or all didn't work. Here are some of the combinations I tried: 1) Fresh install OS X 10.9.5 Mavericks. Install Bootcamp. WORKS 2) Upgrade Mavericks to OS X 10.10 Yosemite leaving Bootcamp unchanged. WORKS. 3) Fresh install of Mavericks. Upgrade Mavericks to Yosemite, then install bootcamp post-upgrade. DOES NOT WORK. 3) Fresh install of Yosemite. Install Bootcamp. DOES NOT WORK. 4) Fresh install of Yosemite. Install Bootcamp using bootcamp disks created under Mavericks. DOES NOT WORK. 5) Install Mavericks. Create bootcamp. Fresh install (not upgrade) of Yosemite onto OS X partition. WORKS (!!!) The one combination I could not get working (the one I want) is Yosemite and Bootcamp using latest Yosemite Bootcamp drivers. So is it Yosemite's bootcamp drivers that breaks the HFS+ driver, or is something about Yosemite itself that breaks the driver. Either way please look into a fix.