No audio... after changing heat sink? (on-board audio, input is ok)

Currently my computer recognizes that there are headphones connected to it(which I have tested on my phone) , the speaker symbol and playback devices shows that the volume is on and active; I have the 6.0.1.6873 Realtek driver and the HD Audio Codec; I have tried changing my default devices in "Playback Devices"; both Windows Audio and Multimedia Class Scheduler are on, and yet I have no sound.

On a side note, every time I reinstall the driver it won't detect my speakers until I set it to AC.97 and, unlike the indicator found in "Playback Devices" the volume mixer is inactive even when sounds should be playing.

I've also tried a system restore to before I installed the heat sink, which is before this occurred, and looking around for audio options in my BIOS (M5A78l-M LX Plus, v.1033) to no avail. The only thing I can think of is to format or somehow v.1034 of my BIOS would do anything even though it was released five months ago and I just got this problem... Please help and thank you in advance.

Also, I've already tried virus scanning and chkdisk, if that is at all relevant.

If you have the RealTek audio and "HD Audio Codec" that usually indicates that along with the RealTek you also have the generic Windows installed HD Audio Codec audio sound driver. If that is the case there can be conflicts and the HD Audio Codec needs to be uninstalled so your RealTek can properly operate.

If this is what's happening, go to the Device Manager, RIGHT click on the HD Audio Codec entry to highlight it and then LEFT click "uninstall". Restart the PC and check to see if the RealTek (and possibly an entry for HDMI audio if you have that) is the only entries in the Device Manager for Sound. The "Speakers" (RealTek) should be set as the default audio playback device in the Control Panel/Hardware and Sound and finally the Sound Panel Playback section.

Yeah sorry, I mentioned the codecs because I thought they were a utility for the drivers, I've only had the Realtek driver.
When I switch this to AC97 in the sound manager:

My Playback devices will look like this(The headphones don't work still)

-When I switch the connector settings to HD Audio my headphones don't work still and they are not detected, does that mean anything?

-Also, when I take all my devices out and put them in one by one, the audio manager doesn't notice me plugging in the headphones.

HD Audio should be the correct type as that is what is on the Motherboard.

As you changed the "heat sink", which I assume is the CPU cooler, what all did you disconnect? If you had the audio disconnected from the motherboard, did you reconnect the HD Audio connector for the front panel (or did you connect the AC97?). The HD Audio is the correct one.

One thing to try. First, uninstall the RealTek in the device manager, DO NOT check the box to uninstall the drivers. Then restart the PC and when Windows starts it will reinstall the sound. If there were a corruption in Windows this will fix it. This also fixes a lot of other flakey problems.

Also check the RealTek HD Audio Manager to see if anything is not set up correctly. On my RealTek HD Audio Manager, Device Advanced Settings, I have an option for how the front panel headphone jack works. See screen shot.

That Audio manager is different than what I have, on both my Gigabyte motherboard (what I posted) and on an ASUS Z77 motherboard. The ASUS has about the same audio manager as my Gigabyte.

The check mark for "Make front and rear output devices playback two different audio streams simultaneously" may be an issue. What different "streams" is it going to playback?

Do you have the latest RealTek driver, for your motherboard, from ASUS? If not, download and install the latest version and see if it changes anything. M5A78L-M LX PLUS - Motherboards - ASUS

Different drivers can provide different options. What you have is way different than all other RealTek HD Audio Manager's I've seen.

The version you have is newer than the latest version on the ASUS site for your motherboard. Where did you get this driver version?

One other issue, you have never addressed my question of the "heat sink". Was this the CPU cooler? What type did you have an what do you have now? As you were working on the motherboard, did you ground yourself (preferably with a "grounding wrist strap") while doing whatever you did? If not, there is a chance static electricity damaged some component on the motherboard.