Windows 7 and avr-g++

We have installed the driver for our new Arduino Uno on a Windows 7 notebook and keep getting the message, "Cannot run program . . . avr-g++ . . . the system cannot find the file specified." error message. I tried copying the file "g++" from the hardware\tools\arv\bin\arv\ path to the path identified in the error message and renaming it "arv-g++" Didn't do any good. Any ideas on how to solve this problem?