You should probably try to separate the vocals and the instruments before you go too much further. If that step fails, then you have no show no matter what else happens.
Vocal Isolation is not a standard tool in Audacity. You might try ...
-Voice Trap
http://www.cloneensemble.com/vt_main.htm
--Extra Boy
http://www.kvraudio.com/get/1651.html
--Kn0ck0ut
http://www.freewebs.com/st3pan0va/
But even before you do that, you should stop using Audacity 1.2.
Audacity 1.2 is very old and no longer supported,
patched, corrected, or updated. Audacity 1.2 can
be unstable on newer computers.
Download and install the latest Audacity 1.3 from here...
http://audacityteam.org/download/
You can install both audacity 1.2 and Audacity 1.3 on
the same computer, but only use one at a time.
Audacity 1.2 will not open projects made on Audacity 1.3.
If you use MP3 or some of the more modern audio
compression formats, get Lame and FFMpeg software
from the same web site. Do not use older software
or software from other web sites, even though they
may have the same names.
Koz
