Short of uninstalling/reinstalling Access, you can't get "factory standards" back, mainly because of what Doc mentioned. Even a full uninstall/reinstall won't guarantee it because, again as Doc mentioned, some settings are database specific (show/hide toolbars, passwords, show/hide objects, etc.).
HOWEVER, if you just open Access proper (with no DB), and create a new blank DB, that's a close to "factory default" as it gets. Some things that affect all of Access (standard file types, for example) will carry over if you changed that. If you just changed the aesthetics (toolbars, colors, etc.), then you'll have to tweak that on your own. Note that "Toolbars" specifically have a "Reset" command button on them that returns them to their original state. If you just need to reset those, then it's straightforward.