Arduino IDE version compatibility with Windows

The IDE recently bumped from 1.0.6 to 1.6.x It has a few differences in the interface including

•  a compile now causes a file save
•  the selection of the Serial port is different (further down) Tools>Port

However, the 1.6.x IDE only runs on 64-bit Windows 7*. To run on 32-bit, you must remain at 1.0.6.

To run Teensy software, it has also been updated recently to catch up. The latest (1.23) runs on IDE v 1.0.6 and 1.6.x 

* Instructions to check for 32bit or 64bit Windows 7 operating system installation.
http://windows.microsoft.com/en-us/windows7/find-out-32-or-64-bit