I stayed on XP until a couple of years ago , then I went to 8 …the only reason I went to 8 was I got a really good deal on a lap top that came W 8 64 bit….if I was more of a computer guy I would have definitely went to W 7 on my own dime on that machine .
then I bumped up my SONAR to X3 PE….before that I was on 6 PE
I think you will probably have a pretty smooth transition since you have been using X1 …
As far as all you work , you should have no problem opening your projects up in the new OS as long as you have SONAR installed …be it X1 or Plat ….you may have to install any 3rd party plugs and synths to maintain the version of the work you have done after you have completed your OS and SONAR upgrade…
I'm not much of a bundle file save guy , can't comment there …I feel most comfortable working w per project folders and saving them as that …
My MO is to back them up and store them on an external drive to archive ….then I have a few hard drives that I went out and got an enclosures for where I can keep my samples , per projects and stream ….
So far I've had very good results opening up older projects from older SONAR versions ( 5 & 6 ) they open up fine exactly as I have saved them in my current version of SONAR X3 and OS …..
all the best ,
Kenny