Session Drummer 3, Toms and the Width Control

Can somebody explain to me why the width control in SD3 affects the stereo positioning of toms?  No other drum instruments are affected by this control in this manner, just toms.
 
I was trying to work out why the low toms were so far right in the stereo field with the pan set to centre.  I thought it was just a 'very asymmetrical' wave file, but then I tweaked the width control and the panning altered.
 
Seems odd to me (?)
 
 

Hmm, might depend on the kit perhaps?  I'm using Sonic Reality's Classic Rock Kit.
 
I'm having some odd panning related issues today.  In addition to the issue in SD3, I'm becoming convinced that the Windows 7's kernel mixer is wired up the wrong way 'round internally (left <-> right).
 
I've mixed down a track where the aforementioned toms are more to the right than the left.  On the master bus if I pan right, the sound goes right and visa-versa as you'd expect.  If I play the mixed-down wave file inside Sonar, same thing; pan right and the sound goes right, toms are on the right.  If I play this file in e.g. Media Player, or the mp3 I've created from it, the opposite is true.  This is through the same soundcard interface, routing via Sonar so I can play with panning etc.  Sonar is still panning right to right, but now the toms are in the left field.  If I play using media player through the MOBO's built in soundcard, I have to switch the RCA connectors the wrong way round for right panning to go right and the toms to be in the right channel. 
 
The only explanation I can think of is that Windows has its left and right the wrong way 'round.  I'm going to play the mp3 file on a few independent devices to corroborate this.

In general, what is the purpose of the width control?

I did a tutorial about five years back that focused on stereo oscillators.  It might help with the explanation of Width.
Wide Load - Stereo Wavetables in Rapture 1.1/LE

"Toms and the Width Control"
 
I just don't get these new fangled band names...