Unless you have inquisitive children or novices using your PC I would not have protected operating system files or extensions for known file types hidden in Windows. Nor would i select the radio button for 'Don't show hidden files folders or drives' in Folder Options>View. What possible rationale there is for wanting .System hidden other than the ineptitude of other users of your PC escapes me.
You can safely copy all the other minor [nonessential] files from another working 1490. Take them from your last backup if you wish, they are unlikely to have been the cause of your problems. If your backup was made after the unit bricked [when file system was made visible by Cure3 fw], be very cautious about copying anything from the folders mentioned by Loly and I previously such as Text, Keyboards, Voice, GPX, POI or detail map images.