Computer model:
HP Pavillion desktop model 500-214
Windows 8.1
IDT High Definition Audio CODEC
(The identical issue exists on my HP Pavillion G Series laptop with Windows 7 and IDT HD Audio CODEC.)
The problem: There are mic and line inputs, but you can't hear them. You cannot hear yourself as you speak or play an instrument into your PC. The meters show input, the audio records, but you cannot hear the live Line/Mic input. Nothing in the Playback/Recording/Levels/Listen tabs changes this. If you are using Skype, your microphone is unheard. If you want to voice chat, sing karaoke, or record guitar, voice or keyboard over a backing track, this is impossible without hearing direct input audio. Windows 95 through XP did not exhibit this issue. Everything from Vista to 8.1 has.
The only way to hear is to click "Listen to this device." This gives you the post-processor sound, which is delayed, and causes a horrendous echo. You cannot time yourself to music, or even carry on a basic conversation, with a constant echo.
Windows 7/8/8.1 users with Realtek audio chips have found registry hacks that bring back the independent Line In/Mic In audio mute and volume slider sets and solve the problem, or are lucky that the Realtek software gets them around the glitch. Those of us with IDT chipsets unfortunately have no such hope.
It is theorized that the Line In/Mic In audio controls still exist in Windows 7/8/8.1 as they did in Windows 95-XP, as proven by the registry hack, but have been removed by HP, Dell and other PC makers for some reason.
Installed software: There is no software that impacts the fundamental ability to plug a mic into the computer and hear yourself. It is not a software-specific issue. I have, however, spent $193 on additional sound cards and interfaces trying to get this basic function back.
Other discussions of same issue:
I've also made two videos demonstrating the problem and my experience with different proposed "fixes," if you'd like me to post them.
I REALLY hope someone with Hewlett-Packard sees this and responds.