Digital BW, The Print

Hope this problem is within the remit of this forum. Please point me 
elsewhere if not!
Just taken delivery of a new computer. I have opted for two graphics 
cards(256 Mb Nvidia Geforce 7800 GTX) linked with SLI for hoped for 
improvement in handling large 16 bit files in Photoshop, along with 
the 2 Gig of RAM operating in Windows XP Home.
The problem I have discovered is that enabling the SLI facility 
disables the dual monitor display, leaving only the primary monitor 
showing anything on screen.I use the second monitor to view Photoshop 
tools and dialog boxes.Disabling SLI restores both monitors. I would 
like to have both if possible! Is there a workaround. Both monitors 
are plugged into one of the graphics cards.
Out of interest, I have timed applying radial blur to a 100 Mb colour 
file, and it takes about 34 secs with SLI both enabled and disabled.
If SLI is disabled, am I only working with one graphics card?
Many thanks
John Fontana