OK, my wife bought a funky looking smooth mouse pad at Borders to use with her wireless optical mouse, PC computer.
The mouse works fine just moving it on the desk top, but on this mouse pad, all directions are backwards! Move it up, cursor goes down. Move it right, cursor goes left.
I tried it with my mouse (same brand and model ) on a different computer and it works just fine.
Any ideas?
Try rotating the mouse pad 180 degrees. I have no idea whether that will work; I just want to see what happens when you do it. It may be that that partcular mouse pad was intended for use in the southern hemisphere.
Perhaps she bought a dap esuom by mistake. 
Shouldn’t that be a pɒd əsnoɯ? 
Paul, it sounds like a problem with the mouse settings, not the new pad. Did you check your mouse control panel?
Why would you use a mouse pad with an optical mouse? Isn’t that like hitching old Bessie up to the horseless carriage?
Well, that’s true, sort of, but it depends what kind of desk you have. If you have one with a high glossy finish, some optical mice go all-of-a-dither. And my computer-desk at home is steel with little holes in, which the optical mouse does not like at all. So both of those situations need a mouse-pad.
And MTGuru’s advice is sound as usual: it’s probably the control-panel settings that need adjusted.
an optical mouse does NOT work well on a flat black lab bench. Trust me, I’ve had that issue quite a lot.
I have used an old shiny mouse pad with an optical mouse that sent the pointer in all sorts of odd directions. It would get hung up on lines on the graphic.
Show off. 
I use a mouse pad, but it’s not for the mouse, it’s for me!
I’m one of the ones that likes a big mouse–my current favorite is the Logitech MX-1100–that you can rest your hand entirely on instead of just dragging it around with your fingertips. As such, the base of my hand rests on the surface that the mouse moves on.
Desktops are hard; mousepads are soft. 
–James
Size isn’t everything. Besides, it’s how you move it that counts.
My thinking about mice has been forever changed . . .