Built-in Microphone no longer Working with Windows 7 on XPS M1530

I originally bought my XPS-M1530 with Vista installed (4 GB Ram).  About a year ago, I did a clean install of Windows 7 Ultimate (32 bit).  I had used the microphone with Skype when Vista was installed but had not tried it with Windows 7 until recently.  It appears to be set up and working and I think drivers are up-to-date but I can record no sound.  I have heard this is a fairly common issue with Windows 7 and was wondering if anyone had any suggestions to get this working.  I have not contacted support yet about this issue.  any suggestions would be appreciated.

Robert Ray