Wow - well I think it's unlikely that both would be bad, especially with the same symptoms. And you've swapped microphones already, and if the same thing happens - it almost has to be down to your sound settings.
Sorry if you've already done this, but I'll post what I would try in your position.
1) Double-Click speaker icon next to clock in Windows
2) Click "Options"... Click "Properties"
3) Select "Adjust volume for Recording"
4) In the window below, make sure the following are checked:
5) Click "OK"
6) Move sliders on all visible levels to 60% or so
7) Click box next to SELECT on "Stereo Mix" slider.
8) If you have an "Advanced" button under the Microphone slider, click it - If you have an option there for "Mic Boost" then make sure it is checked, then close the Advanced window
9) Click the "X" to close the Recording controls property.
Now you're back at the desktop - Double-click the speaker again. Go to "Options" - "Properties"
Make sure in the Playback options that you have checked:
- Line In
Then click "OK"
Now you're back at the playback mixer, boost Volume, Wave, Line In and Microphone volume sliders to max. Make sure "Mute" isn't checked on any of those four. Close.
Repeat your test with the Sound Recorder. See if it's any better. If not, physically unplug your microphone from the "Mic" jack on the sound card and plug it into "Line In" and do another test with Sound Recorder.
Hope this makes sense, and if you haven't tried it, maybe it will fix it.