TheSpoopyGhost

My friend asked me to build him a new desktop computer that replaced his old laptop, but when it was finished he was complaining that he couldn't plug his headset into the headphone jack and use the microphone. After explaining that the two are separate jacks and one gives output and the other takes input, he brought out his laptop with two separate jacks for headphone and microphone, then proceeded to plug the headset into the headphone jack only and his microphone worked. I'm not sure on the exact model of the laptop he was using, but he was using an MSI stealth laptop with a GTX 1060 that cost around $1000. What would explain why he was able to plug his headset into the headphone jack and have it work? I can post pictures later today, but I'm not in my dorm room at the moment.

I mainly use this machine for playing games, I guess it would make sense to try and get a GPU first then

I've got a i5-8400 cpu and a gtx 1070. To my knowledge those are pretty well matched so I was wondering which I should upgrade first or if it even mattered and I should just basically flip a coin.