Windows 7 has a frustrating bug – at times, the volume drops dramatically for no apparent reason, everything is working fine except when you plugged in your speakers the volume is very low no matter if its video stream or windows sounds. The most annoying thing with the low volume problem is the fact that even on reboot; the problem might just refuse to go away and may bother you endlessly. To Fix Sound Issues in Microsoft Windows 7 you need proper troubleshooting or windows 7 support guide.
It turns out this problem is caused by a feature in Windows 7 that is intended to soften the volume when communication activity is detected. Find solution on this Windows 7 support blog, how you can fix this annoying bug in just a few minutes with few easy steps -
Step 1: Go to Control Panel from 'Start -> Control Panel -> Hardware & Sound -> Sound' and click on 'Sound'.
Step 2: 'Sound' dialogue box will be opened. Now click on 'Communications' tab and select last radio button option 'Do Nothing'.
Step 3: Now Click 'OK' to apply the changes and close the dialogue box.
Also find here how to fix if sound not working on dell laptop.
The operation is as simple as the instructions above and it worked for me. The sound problem is one little aspect of Windows 7 that can cause you unnecessary heartache if you do not know how to troubleshoot it. But here I have given you a simple procedure that should see your volume up and running in a matter of seconds.