Depending on which type of audio device you want to use, you must select and confirm to a popup when plugging in your device in order for the system to recognize it.  If needed, a proper adapter can resolve your issue as well.  For example, if you use a headset with 2 separate plugs and you want to use the input port at the front of machine, you might need an adapter which can take both connectors. [IMAGE] On the back of your machine, there is a light green port (#10 in picture), it is used for output only, such as external speaker, headphone, audio-out. [IMAGE] At the front of your computer, there is an input port (#3 in picture), which can be used for multi devices such as headphone, headset, microphone, audio line-in.  Each time you use this port, a popup on screen asking to confirm, you must select the correct type of device and hit OK. [IMAGE]  For your case, after plugging in the microphone, the popup might ask you to select mic-in or line-in, just select mic-in and hit ok.  That should allow the mic to work. As for your inquiry about a PCI sound card, it is a legacy type, if you find one that works, it may not be much better performance than the built-in.  
I am trying to do screen recording. But the software tells me there is no microphone. Is this true? if yes, how to add a microphone?
Precision 3630 doesn't have microphone?