Read the track list. This means you have the song multi-tracked and have control over each individual track. If there is not a list or labels, hit "Mute" or "Solo" on each track until you find which track is the guitar. Keep it muted, and the guitar is gone. This is the only 100 percent sure way to remove a lead guitar track, but it requires having the master tracks.
Hook up as large a multi-band equalizer as you have access to. Guitar tracks are recorded in the mid-high to high range, located on the right side of the EQ. Start pulling down frequencies one by one. The guitars will become muted when certain frequencies are turned down. This will affect all the music, the guitar reduction will not be perfect, and the remaining tracks will be left without the frequencies turned off.
Pan your balance knob to either side. Does the guitar disappear when you do it? If the lead guitar is panned in one side, it will be removed as easily as panning completely to the right or left. You can rerecord your track using only one side and have no guitar. Most often, however, lead guitars are not panned completely to one side.
Download the winamp plugin DSP Center Cut. Using this software, all tracks that are panned to the center of the track will be removed. Most often this is lead guitars and vocals. The unfortunate result could be the loss of vocals; nevertheless, there is no other way currently on the market.