Built in mic not working after formatting windows

Method 1: Try running the Recording Audio troubleshooter.

1.     Open the Recording Audio troubleshooter by clicking the Start button , and then 

2.     Clicking Control Panel. In the search box, type troubleshooter, and then

3.     Click Troubleshooting.

4.     Under Hardware and Sound, click Troubleshoot audio recording.‌ 

5.     If you're prompted for an administrator password or confirmation, type the password or provide confirmation.

Method 2: Follow these steps..

Step1:  Check if the microphone is enabled.

1.     Click on ‘Start’ button and select ‘Control Panel’. 

2.     Click on ‘Hardware and Sound’.

3.     Click on ‘Sound’.

4.     Open the ‘Recording’ tab.

5.     Right-click on free space and select the following options.

o    Show Disabled Devices 

o    Show Disconnected Devices

6.     Now check if your microphone is enabled. (You may have to right-click on it and select Enable to enable it)

Step 2: If the microphone input level is too low, make sure the microphone input level is set properly.
To adjust the microphone input level

1.     Open Sound by clicking the ‘Start’ button, and then clicking ‘Control Panel’.

2.     In the search box, type ‘sound’, and then click ‘Sound’. 

3.     Click the ‘Recording’ tab.

4.     Double-click the microphone that you use for Speech Recognition.

5.     Click the ‘Levels’ tab, and then use the slider to set the input level for your microphone.

Please make sure the Microphone properties are set properly and check if that fixes the issue.