Welcome to the Forum!
Sorry to hear of your problem with W10->W7 reversion. Reversion problems are quite common. Just to facilitate us helping you, can you tell us the Make/Model of your PC or laptop?
Next, did you attempt to do the W10->W7 reversion using the Microsoft tool to do so? Or did you completely reinstall W7 on your hard drive after erasing W10? This is a very important question. If you attempted to do the reversion to your original W7 and it's been more than 31 days since you performed the W10 upgrade on that computer, you could have a failed reversion attempt. Microsoft only allows you to run the reversion to your original Windows version within that time period. If this is the case, then I have some suggestions that will fix it.
Also, you don't mention whether the Win7 you reverted to is working in all other aspects; i.e.: able to browse websites on the Internet, E-mail, type and read documents (Word, PDF, Excel, etc.); use photo editing software, gaming, etc. I'm guessing from your post that the iTunes is the only thing that is not working, correct? Yes or No here, please.
From your description of the file properties, it sounds like something did get scrambled in your Windows. A screenshot would be most helpful, as text only is subject to interpretation and iffy at best. A proper path to your iTunes folder or files would look like this (taken from my W10 system):
C:\Users\bigbe\Music\iTunes\iTunes Music\Music\Fleetwood Mac\Rumours
Notice that the Path should start with your Windows login account or user name under the C:\Users folder. In my case, my full user name is:
"bigbearjedi", but the name on my Windows login screen is actually
"Marc Lastname". W10 truncates the E-mail address of my Microsoft Account (in this case it's
"[email protected]"). Therefore, W10 shows the path
C:\Users\bigbe...\Rumours, where C:\Users\bigbe takes the
"bigbe" first 5 letters of my Microsoft account E-mail address and truncates it.
This can be tricky, as if your Windows login or username is 5 characters or less in W7/W8x, such as
C:\Users\Bob, for instance, there is no truncation of the username. In W10, the truncation occurs whether or not you have a Local Login or a Microsoft Login for W10. The distinction here, in case you are not aware, is that one needs to have a valid E-mail address associated to their Microsoft account or have a valid Microsoft native E-mail or LiveID account, such as a Hotmail.com or Outlook.com E-mail address. If one is therefore doing this, their intention is to get access to all the Apps in the Microsoft App Store and can purchase or download apps from the MS App Store as well as access all other Microsoft resources.
In Win7, there is no default User name called:
"OS" or
"C:\OS", unless you physically entered
"OS" or
"C:\OS" when you first setup your computer out of the box, or went to
USER ACCOUNTS in Control Panel and added that username. From your description, I'm going to guess that your name isn't
"OS" or
"C:\OS", and that means that your W7 is corrupted, either do to the reversion process being incorrectly applied, or if you attempted the reversion process outside of the 31 day limit imposed by Microsoft as described above.
This may be more information than you wanted; but I find it helps to explain what I see as the problem, so you can understand what's happening or has happened to your computer.
Until I get more information back from you on my questions, I would recommend you backup
ALL YOUR PERSONAL DATA ON THAT COMPUTER TO EXTERNAL MEDIA FIRST, and then perform a Windows Reset using factory recovery media (Discs or USB), or from built-in partition on the hard drive. This will correct your iTunes problem (as well as any other problems with the post W7 reversion windows) that might have occurred. Subsequent to the Windows reset, you will need to download/reinstall any and all programs that you added to your computer after your first purchased it from the Internet or Disc/USB as they will be completely erased by the Reset process. Once your W7 has been reset and everything is working, especially the Internet, you can then restore or copy back your data from the external media you backed it up to as required above. At this point, you can reinstall your iTunes on W7 and all should work.
Pay particular attention to the Username now showing in your Path to the Music folder. Again, if your userame is
"Bob", this should now be
"C:\Users\Bob\Music\iTunes\iTunes Music\Music\Artist Name\Songname".
Let us know how it goes.
Best of luck,
<<<BIGBEARJEDI>>> 
