compatibility of Inquisit 1.27 and XP?

I've been having problems running inquisit programs (for example, the sample from the website) on some new XP computers. The program runs, but extremely slowly (it takes about 4-5 seconds for each trial to appear on the screen - obviously, this means it's useless for reaction times!). I'm wondering if this could be a compatibility problem, since I have version 1.27. If 1.27 is the problem, do you have discounts for upgrading to 1.33? Thanks!

Inquisit 1.27 was released when XP was just a twinkle in Bill Gate's eye, so you'll want to install Inquist 1.33 for XP support. The upgrade from 1.27 to 1.33 is totall free. -Sean