MrC's suggestion should work the same on files and folders.
It probably won't filter out Unicode characters, though. (Unless I'm confused about what it's doing, it's filtering out characters in the 0x20 to 0x7e range, but lots of non-English characters are way above that range in Unicode.)
If the problem is the characters themselves and not whether they are in a file or a folder name, try the alternative. Various simple rename presets, #5: Make Safe Name.