[samuraibunny]

I had the same problem when I upgraded my server to windows 10 - my HTPC could no longer access the shares.

It turned out that the guest account status is turned off in Win 10 as a security measure. When I turned it back on everything was as before.

Have a look at the Guest account status using the Local Group Policy Editor
Run gpedit.msc and then navigate to:

Computer Configuration - Windows Settings - Security Settings - Local Policies - Security Options - Account: Guest account status

Make sure it is enabled

If you don't have Windows 10 Pro but rather Windows 10 Home (like myself), which doesn't have gpedit.msc available, you can enable successful sharing by disabling password-protected sharing for guest accounts as follows:

1. Go to Control Panel\All Control Panel Items\Network and Sharing Center\Advanced sharing settings
   
2. Scroll down to All Networks
   
3. Scroll down to Password protected sharing
   
4. Select the Turn off password protected sharing
   
5. Click on Save changes
   

Also, I noticed that you (unfortunately) cannot have your main administrator account set up with your Microsoft account - you have to create a local admin account and add share permissions for that account specifically (you may be able to add an additional local administrator account and give that particular account the necessary permissions, but I'm too tired/lazy to go test that now).

Bob's your uncle and stuff.