PK-Tether is a piece of crap. I've tried it on 3 different Windows systems, all with progressively increasing amounts of RAM (4Gig - 32Gig). 2 pictures, crashes constantly, controls do not work on K-x cameras, and the interface is garbage.
LightRoom has NO support for Pentax cameras.
Capture One, from Phase I has NO support for Pentax cameras, despite what the install log reports.
Basically, I'm sorry to report, but those of us that use Pentax cameras are SOL when it comes to tethering software. I wish I could report happier news, but if you don't own a Canon or Nikon, you're pretty much screwed in the tethering department.
That said, LightRoom is fantastic for post production off the media cards.