Dell 5150 E510 Mic drivers need to be continually installed

I have a Dell 5150, windows XP Home, with both front and rear mic ports. I use Yahoo chat to keep in contact with distant family. However each time I boot the system I have to reload the drivers to get either mic port to work. Dell support was no help – their response was to replace the m/b and or to reload the o/s — neither worked. I see no pings in device manager and nothing pops up when I run diagnostics. Does anyone know how to overcome this nuisance. Thanks for any help!