I recommend booting up a Linux "LiveCD" distribution. It will detect your video and microphone devices and install Linux drivers. Since it runs directly off a CD or USB flash drive, you need not make any changes to your Windows installation.
If the symptoms you report in your OP persist under the new Linux OS, it is likely they are caused by hardware problems and you'll need to RMA your laptop to get them repaired.
If the problems disappear under Linux, a good, clean Windows installation (or the less appealing ASUS Factory Recovery) might be all that's needed. Alternatively, some driver cleanup with CCleaner may allow you to skip a complete Windows installation.
G74SX-A1 - stock hardware - BIOS 202 - 2nd Monitor VISIO VF551XVT