Tony,
It's difficult to diagnose without hearing the end result. If you could post one of the recordings, then I may be able to help.

One of the first things I would do is burn the recording onto a CD, then listen to it using the CD player in your car or something other than through the computer's sound system. If you still hear the same, muddy recording, it will be a process of elimination to determine where the problem orriginates.

It is possible that your recording software may be the culprit. You can check this by going to www.goldwave.com and downloading the shareware version of GoldWave and re-record one of the songs to see if the same problem persists. Again, make sure you burn the song on a CD and listen to it on something other than the computer.

Another frequent culprit is the graphic equalizer settings of the mixer. Essentially, they should should be somewhat crisp, with some emphasis on the high and low end, and the mid range just a little above flat--kinda' like a smile.

If at all possible, record your vocals dry and add any effects in the editing process. There are times when reverb and echo are really detrimental to the recording phase.

Hope this is of some help,

Gary