Are you talking about Power On/Off discrete codes? When I added my Xbox360 using model based setup in NevoStudio Pro. I put "Microsoft" as the brand name and just entered in "360" as the model number. I selected the "Video Accessory" version.

The only problem is that there are no discrete Power On/Off commands given to you. I got those by finding hex commands here on remotecentral in the Pronto / Hex code section. Once I copied and pasted the discrete power commands from the web site, I could turn on and off my Xbox 360 with ease.