You wrote about the external but didn't tell if the enter key worked or not on the external.
Ive tried every basic method to reactivate/fix the enter key on my laptop(there is no second enter key). I've un/re-installed my keyboard driver, checked for updates, tried remapping programs like sharpkeys and keytweaks. i've even used external keyboards(which work exactly like my normal keyboard but without the enter key functioning) I'm lead to believe that somehow my enter key has been disabled. At this point all I can think of is a registry edit, but I'm clueless as to how to do it, or if it would even be appropriate in my situation. I'm willing to provide computer settings if necessary, whatever is needed to fix this irritating issue.

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