1.6.4 Windows 7 - USB Drivers?

Very frustrating. I "upgraded" to 1.6.4. Probably a mistake.

So it uninstalled 1.6.3 and not it can't find USB drivers.

For what it's worth the quality of the IDE install is unaceptable. Even though it'd free it's not worth it. If you are going to put out a product - even if it's free - it should at least install.

I know it is frustrating.

Happily for me I started with Visual Studio 2013 Community edition which has support for Arduino but you need another extension. It immediately recognized the Arduino Uno without any problem. However the Arduino Uno IDE was not that easy. It requires drivers.

I have couple of posts on Arduino IDE, Arduino With Visual Studio etc. Look up my blog and search for 'Arduino'.

Good luck