USB Blaster driver was installed, but Altera Programmer Hardware Setup can't find it.

Part of the issue is there are actually 3 drivers that need to be installed. The first driver makes the device show up as "USB Blaster". The second two drivers are virtual to make the JTAG device appear - essentially the blaster suddenly appears as two devices instead of 1.

If you install the driver manually pointing to the USB blaster directory it tends to only install one of the drivers. Instead if you point to the "C:\altera\15.0\quartus\drivers\" folder and check the box to include subdirectories, it should install fine. I've never had any problems getting it to install in this way.