On the new laptop with Win 8.1 it stuffs it in the C:\programsx86\ folder. But I also tried it on my trusty Vaio running XP with same result. Both laptops also have software,routines, IDE & USB drivers for 4D Systems displays that also use the Arduino IDE. That is the only recent change/addition I can think of.
My last desperate step is going to be putting a virgin Arduino IDE on another laptop running XP that has never had either, then try to compile. That does not make sense to me though because I thought compile is entirely an internal event between the IDE and the sketch folder. Is there anything in the IDE other than MEGA 2560 and COM port to set or check?
when you connect to your RAMBo what device is showing up in the device manager connected to usb?