Chithead,
While it IS possible to program an M1225 with a USB programming cable, they play best with a computer with a real RS-232 serial port.
That being said, if that is not an option for you ( which it sounds like that is the case) they play best with a Windows XP computer using the USB cable.
I *may* have programmed one of mine with a Win 7 system, but ( and, my memory is pretty foggy on this) it did not like it and it sucked.
I have a dedicated XP laptop with a serial port that I use for programming all of my /\/\ stuff now, so it's no longer an issue, but the first computer I used to program my M1225's was an Asus EeePC Netbook running XP home, with a serial to USB adapter and a serial cable. You WILL have to play around in Device Manager to get the port settings right.
The RSS is pretty self explanatory and very straightforward, if you can get a legitimate copy of it.
I hope this helps you out some.