FnR means flatten and rebuild, which is referring to the operating system (OS). This is a common acronym used in Ops [since they do it so damned often] to describe formatting [and perhaps partitioning] a computer then reinstalling a 'clean' OS. In layman's terms, this drains the evil and let's you start over. 
But the Zune software is heavily tied to your music/video/picture libraries, especially if you have downloaded or subscription content with those nasty little DRM licenses attached. So here's a question I often see on our internal Zune discussion list:
How do I maintain my Zune library if I need to rebuild or reinstall my operating system (i.e.: Windows XP or Vista)?
There is actually a method for doing this built right in to the Zune software. Go to Marketplace...Downloads...[Purchased or Subscription]...[Songs or Videos] and select "restore all". But if you have hundreds or thousands of songs downloaded [as I do] it will take quite a bit of time to download them all again. Add that to the time it takes to sync 30+ GB and you've got yourself a full day ahead. Go get some coffee.
For the typical computer enthusiast (aka: geek) it's quite simple to avoid that step. I've done it a handful of times over the past year and only encountered a few minor glitches. I recently went through the process again and took notes, so here ya go. It looks long, but it's simple really.
Before uninstalling Zune software (or flattening your OS):
- Backup (copy) all of the following directories:
- From:
- C:\Users\YourName\Music\Zune [includes Playlists, Podcasts, Received Pictures, Subscription and Videos]
- C:\Users\YourName\Pictures\
- Note: These are the default locations for your "Documents" path assigned automatically by Windows Vista. They will be slightly different for Windows XP or if you have changed the location of your "My Documents" folders.
- To: A folder on another (logical or physical) drive that won't be affected by whatever you're doing (e.g.: don't just copy them to another folder on a drive you're about to format...tsk, tsk, tsk).
Now feel free to do what you gotta do. Uninstall, format, partition, pray to the Vista gods, yada-yada-yada. 
After installing new Zune software (or installing your new OS):
- Update Monitored folders:
- If you want to leave the default settings, then you need to copy the backups you made earlier to C:\Users\YourName\Music\Zune (again, this is Vista's default location for your "Documents" which will be different for Windows XP*).
- If you want your files/folders in a non-default location [my preferred config] then you need to tell the Zune software where to look:
- Go to Settings...Collection...Monitored folders.
- For each category [Music, Video, Pictures & Podcast] select “Add Folder”.
- Browse to the folders where the respective content is located (e.g.: D:\Users\Tod\Music\Zune).
- I then remove the default folders so I don't get any 'extra' crap being synchronized.
- Plug in your Zune. It should be automatically detected and take you to the settings screens:
- Note: These steps assume your linking the Zune to this computer as it's primary (aka: home PC), not a guest.
- Linking screen - Select “Link your Zune to this computer….”
- Name your Zune screen – If you previously named your Zune then just leave it alone and select “Next”. If you want to rename your Zune, then do it here.
- Sync Options screen – Make the choices that make sense to you.
- Select Finish and your Zune will start syncing.
- If you have downloaded or subscription content then you will need to login in order to authorize the DRM stuff during sync.
That should be about it. Normally I don't have to do anything special, but this last time a few videos I purchased [my 4 year-old daughter loves Foo Fighters vids 
] wouldn't synchronize, so here's what to do.
DRM'ed content won't sync:
- In the Zune software, go to Marketplace...Downloads...[Purchased or Subscription]...[Songs or Videos].
- It will start retrieving your download history, which might take awhile if you have a butt-load of songs. I have a few thousand songs via the Subscription and in 2-3 minutes it only downloaded 10%.
- Select "restore all".
Unfortunately, that didn't work for my purchased videos, so I had to delete them from my PC first.
- In the Zune software, go to Collection...[Music or Videos].
- Select the content that refuses to sync or reauthorize.
- Right-click...Delete.
- Select "Delete file(s) and remove from collection".
- Note: If you select the default option to "Keep file(s) but remove from collection" you'll end up with 2 files on your PC.
- Then go back to the "restore all" steps above and try again.
Note that this method would also work if you just want to move your Zune collection to a new PC. Depending on your internet pipe, it should be faster to copy/paste your content files from PC to PC then to re-download them through the Zune software. Once you run Zune, add the files to your collection and sign in it will authorize all of your DRM'ed stuff.
You should be golden now. Happy listening!
~tod
* Windows XP default location is C:\Documents and Settings\[YourUserName]\My Documents\My Music\Zune\