Can you upgrade your iOS device on a computer that it is not synced to?

My wife never syncs her phone to her laptop, which I rarely have access to, but I would like upgrade the version of her phone's iOS when updates come out.

Is it possible to plug her phone into my computer (a MacBook) and upgrade the OS whilst preserving all of her settings/music/etc, even if her laptop is a Windows 7 PC? Further, even if this is possible is it advisable?

Yes you can.

It's not a smooth process, since that computer will back up all the data and app packages for all your apps, then restore that backup data but it won't have the apps or music that doesn't get backed up as part of the backup process.

It will work, but you might want to transfer purchases / authorize that computer for a more transparent upgrade process. You can't really know it worked if you don't reload the apps after you restore your "backup".

There's nothing preventing you from doing this and then restoring your backup when your upgraded phone gets back to the computer from the last backup. You have to keep track of things and not do work that will get wiped when you load an older backup, but I've done this many, many times and it works well when you understand a bit how backups work.

• iPhone and iPod touch: About backups

Fairly sure this is not possible. Your computer will detect it (the iPhone) as new device and will want to sync it or set it up as a new device, before you even get the option to start the software update.