where have my music and podcast libraries gone

If the music is missing too for pensioner15 then it sounds more like a corrupted database. See Re: Why did iTunes 11.1 (126) delete all (SEVERAL HUNDRED) Podcasts? for another example of the unwanted side effects of syncing podcast settings. From the sound of it you've already done things that mean you're unlikely to be able to recover erased files, but at least you have a somewhat outdated backup. See Backup your iTunes for Windows library with SyncToy to protect your library in future.

tt2

I noticed it change the path of where my itunes directory was (I have it on D: the default is C:) - I re-pointed itunes to where my folder is and still nothing is populating, no media files or apps. I'm waiting to enter my phone # for tech support to call me, but I'm sure it's jam packed with people like us.

Did you tick the option to synchronise your subscribed podcasts?

I did that when running iTunes 12.7 for the first time and this happened to me. I suspect when you synchronise the podcasts, those you didn't subscribe to via the App Store (i.e. you subscribed to them using a RSS feed) get wiped since they are not registered in Apple's database (and thus there is no record of a podcast on the Apple side to synchronise with)

It's almost certainly not a corrupted library issue because the podcast files disappeared too (and iTunes didn't even have the grace to put them in my Recycle Bin - they just outright disappeared)

I went through one round of restoring podcasts by resubscribing to the podcasts for which empty folders were left (even if the podcast files inside were missing), but some directories (with files inside) were deleted too. Go figure. Lucky I have a 5 month old backup

Thanks.

Normally I backup every month but this time I procrastinated because I needed to restore mail files from an older backup.

No harm done I think but yeah frequent backups are better.

Thanks for the SyncToy suggestion but I'm running low on HDD space. Just need to backup more frequently! The important stuff goes into the cloud anyway.

On a related note something similar has happened in the past when I changed my App Store to a different country and then back to the original one

I think switching the country forces a sync, so hopefully disabling synchronisation will prevent this issue (I might test this - AFTER making a backup)

See Empty/corrupt iTunes library after upgrade/crash.

tt2