You might try http://www.pentax.com and click on the country of your
choice or the country where you live and the Pentax HQ might have
the drivers listed.
It's not as easy as my Olympus D-510 was. All I did was plug it in, and it showed up as a drive. I don't know how Olympus made it that easy and no one else has. But the Optio required popping in the driver's CD. I just used the one that came with the camera. It installed all the required drivers. And now anytime I plug in the camera to the USB port, it shows up as a drive. Works just like the Olympus, only the Olympus didn't need a driver and the Optio does. The driver that came with the camera should work fine. I don't know if it works optimally, but I haven't had a problem with it. And it's FAST too.
--Shawn