In fact, it wasn't just the enter key that was malfunctioning as other keys, such as the volume control and backspace were not functioning correctly and performing the tasks of other keys.
Initially I thought that the laptop was broken, as it was 3 1/2 years old and in a fairly bad state due to it being dropped a couple of years ago. Also add the fact that my friendly cat loves to walk over the keyboard every time I use it, I thought that she perhaps had caused the keyboard to go completely cuckoo.
Naturally, I didn't give up and tried several things to rectify the problem. 1st thing I did was the trusty turn the computer off and then back on several times. Unfortunately that didn't solve the problem and the keys were still malfunctioning. 2nd thing I did was to gently remove the enter key from the keyboard so I could view the underneath and check for any gunk that had built up over the years. There was a little bit of gunk, but I cleaned that off and the problem still persisted.
By now, it was time to do an Internet search and see if other computer users were suffering the same problem. They were but the search results that Google gave me were frustrating and of no help to myself.
The only advice and probable cause I could find through a Internet search, was that the language of my keyboard had been changed, (example from UK English to Italian). Okay, that sounded spot-on, so it was time to find the keyboard settings and see if the language had been changed.
To do this in Windows 10 you click on the Windows icon in the bottom left-hand corner, then select Settings > Time & Language and then select Region & Language from the left-hand side menu. You are then given the option to select your country or region, such as the United Kingdom. By default, mine should have been sent to the United Kingdom which it was. So, it appeared the problem wasn't to do with the language settings. However, I tried setting it to the United States to see if that had any effect on the malfunctioning keys.
Sadly it didn't.
By now, I truly believe that the keyboard was broken and beyond repair. Or at least it wasn't worth even attempting to repair a laptop that was already in a bad condition. However, I tried one more thing, and that was to run a malware/virus scan using Malwarebytes Anti-Malware, which is a great free program that scans your computer for malicious software.
Before running the scan I made sure that Malwarebytes Anti-Malware was fully up-to-date with the latest database version. Next step was to perform a system scan which can take quite a long time, depending on how many files and programs you have on your computer. Mine took approximately one hour or so. After the scan, several malicious programs were detected, which initially weren't of any great concern as virus/malware programs often detect a few programs which are completely benign.
So, I decided to delete the ones that it had detected did a compulsory restart of the PC, cross my fingers and hope for the best. Upon the restart, I immediately opened WordPad typed a few words hit the enter key and bingo, it worked perfectly. The enter (and other keys) were all working correctly and no longer performing the tasks of other keys.
It was a malicious software program that was causing the problem all along. Not quite sure how it got there, since the laptop in question is used by several other members of my family, but it had nothing to do with language or other settings within Windows.
If you are also experiencing the same problem, then it's definitely worth following these steps. 1st thing I would do is check the language setting within Windows. I've already explained how you do this in Windows 10, but if you're running on an older version of Windows, I believe you can change the keyboard language setting from the Control Panel and then look for and select Language and Region and make sure it's set to your default language (example, English (United Kingdom).
If that fails, then run a malware/virus scan using a program such as Malwarebytes Anti-Malware. If that program doesn't detect any malicious software programs then try using a different virus or malware scanner. You can find a list of free antivirus and malware programs at the following page.
If you do find that it was a malicious virus that was causing the keyboard problem, It's a good idea to change your password/s that you use on sensitive sites such as your bank or shopping accounts, et cetera, just to be on the safe side.