Hi HogJam,
We hope your issue has been resolved, if you've found solution by yourself. We would appreciate it if you could share with us and we will mark it as answer.
The N edition does not have the multimedia functionality. That is why Microsoft released the Media Feature Pack (KB968211), which is specifically for adding the multimedia functionality into the N and KN versions.
Lots of same cases has been reported, but unfortunately seems like no straightforward pills, many users ended up with fresh install. I checked their CBS log but has no errors at all.
Id suggest try using a fresh install since you mentioned that you have service pack 1 installed already.
http://download.microsoft.com/download/B/9/B/B9BED058-8669-490E-BA61-D502E4E8BEB1/Windows6.1-KB968211-x64-RefreshPkg.msu
If you just need Windows media play for GTA V, Manufacturers such as Steam has workaround for that and I think you have found that already.
Still I will keep digging that issue hope we will have some good news for you.
Regards,
D. Wu