Check the folders NTFS permissions in the folder/file security tab. Even if the everyone group has full permissions on the share - NTFS permissions can produce an access denied if they are more restrictive than the share permissions .i.e in this case No Access - Or it could be assigned groups and users
For example:
Folder1 {Share permissions Read/Write} - {NTFS permissions Read} then the user will only get read as the most restrictive permissions apply.
If this is a home network and you don't mind everyone getting to the folders then I would just add "Authenticated Users" - Modify - to the NTFS permissions.
You can also try:
Control Panel
Administrative Tools
Local Security Policy
+ Local Policies
+ Security Options
Network Access: Do not allow anonymous enumeration of SAM account, and shares. (Enabled) - It Should Be Disabled.