I am not sure this is a Windows 7 issue or some sort of virus/malware. I am experiencing the problem on HP G60 Laptop. The problem began yesterday while listening to music online. As soon as I hit the volume icon in the bottom tray, the level bar that appears moves down to mute (by itself). I can manually use the key to turn the volume up again but as soon as I hit the icon, the volume starts decreasing. Similarly, when I access the speaker properties, the "level" bars move by themselves, either increase or decrease. Lastly, and I am not sure it is related, all the drop down menus in Mozilla Firefox are locked. I try to move the cursor into the box or drop down the menu but only appears for a split second. I've already run Avast, Malwarebytes, and Super Anti-spyware. Please help.

Check your system files as per instructions here:

SFC /SCANNOW Command - System File Checker - Windows 7 Forums

Thanks for you response. I figured it out by accident. I did not realize my son had dropped the mouse (wireless) and that was causing the volume and drop down menu malfunctions. As soon as I unplugged it and used the mouse pad on my laptop, the "light bulb" went on. This information might help others, as I assumed the mouse continued to work properly with the exceptions mentioned above. Just purchase a new mouse and everything is back to normal.

Thank you for that valuable feedback on a potential causal factor that is often very less obvious.

Certainly, others will most likely benefit from your 'accidental discovery'.