Is there a way to transfer files between different software's so that all the different tracks stay separate? I'm trying to get a lead guitar track from my brother who lives a couple states away and I was hoping to get a lead track from him but still have it on it's own track(s) isolated from everything else for mixing purposes. The main issue I'm worried about is he has windows 7 & I have windows 8. Is this possible?

The version of operating system you are using should be irrelevant in this scenario.

You aren't saying much about your environment. If you both have sonar just send a bundle file or export the track to wav for import. Wave import/export will work with any software regardless.

Otherwise need more info. Most people record on isolated tracks.

If the operating systems don't apply to this then I'm golden. He's gonna have the same software (Sonar X3) as me so I will be sending him the bundle.
And I guess I don't understand the term "environment" and to what it applies to. Can you guide me to a page in the index? I am kind of new but I've been learning new stuff as I go.

Environment in this context just means "the combination of operating system and software that you're using"

When trading SONAR projects, the more important difference between "environments" is audio and MIDI hardware and drivers. Chances are each of you will be prompted to select appropriate audio (and MIDI, if applicable) outputs each time you open the other's saved copy of the project, but it should be fairly obvious what you need to do. You'll also want to make sure you're running the same sample clock rate on your interface. But SONAR should be able to switch it for you in most cases, and chances are you're both defaulting to 44.1kHz.

Swapping entire projects is time-consuming, since larger projects can quickly become several gigabytes in size.
 
If your brother is doing only that one guitar track, the easiest method is for you to send him an MP3 of the full mix that he can import into his own project.
 
Then, when he's ready to send you his part all he has to do is mute the full mix and export from 00:00:00. Now he only has to send you maybe a 50 MB file that will sync up perfectly to your project when you drop it in at 00:00:00.
 
Because there will be a lot of silence at the beginning of his file, he'll be able to zip it up and make it even smaller, suitable for an email attachment.

Good point Bitflipper. Also, I don't want to give raw tracks to anybody else to manipulate.