Hopefully this will save other Arduino Newbies some angst...
I struggled mightily to get a new Arduino Nan V3.0 board (generic from HobbyKing) to talk to my Windows 8.1 laptop. The infamous:
avrdude: stk500_getsync(): not in sync: resp=0x00
The board played nicely with my Mac OSX install. The Win 8.1 install talked to my Uno board. Eventually tracked it down to a Win driver issue. The version of the FTDI driver installed from either current Arduino IDE release 1.0.5 or the 1.5 beta didn’t work. Updating to the latest FTDI drivers: 2.10.0 1/27/2014, didn’t help.
“Updating” to older FTDI drivers: 18.104.22.168 4/10/2012 solved the problem.
Finding the older driver is tricky, but this worked for me: