ok, in your system tray there will be a speaker double click it. you will see a mixer popup with a bunch of adjustments. in that window, click options, properties.
in the dialog that pops up select the "recording" radio button, make sure the "microphone" box is checked, and press "ok"
this is your microphone input level.
In this window you can click "options" "advanced controls"
after you do this a button will appear under the microphone volume, click it.
here you can adjust more options such as Mic Boost. You can select this for a 20 db boost.
After doing this, you may want to check skype for a "do not modify my mixer" or "do not change my audio" setting, as with Yahoo Messenger. I prefer using this because it seems that yahoo always wants to turn my mic all the way down.
if the speaker isnt in the tray:you can do this