Hello and thank you to all that read this to offer assistance. My issue has been one that I have reached out to Google for and have yet to find any suggestion that actually works including a fresh install of my audio driver.
The issue is I have a Dell XPS L521X with Windows 7 Professional (64-bit) with a built-in microphone that shows up just fine in my recording device area for enabling/disabling, changing settings of in Dell Audio and what have you, but when I plug in an external mic the computer does not even recognize the fact it has been plugged in by updating my recording devices list or giving me the option to switch to it in Dell Audio etc. The external mic I am trying to use is a Logitech H250 gaming headset which has one cord that then splits into two 3.5mm plugs - one for the headphone jack and one for the microphone jack. Sound comes through perfectly clear through the headphones and I am able to change the settings between my built in laptop speakers to sound coming through the headphones but the laptop just does not recognize the mic plug no matter what I try; The most that happens is an information pop-up that says "You just plugged a device into the audio jack.".
The laptop is only 1.5 months old and the headset is under 2 years old but still works perfectly fine on any other computer I try, including my previous Windows 7 laptop from Asus. On this Dell I used Piriform Speccy to get my laptops exact details and everything listed under Sound Cards is Realtek High Definition Audio, Bluetooth Audio Device, and Intel Display Audio.