It is XP... I am in discussion with the shop that built this PC, unfortunatley they suggest we wait to hear from Curious Labs... I've had nothing from them in 2 months despite numerous e-mails and forms to technical support... Is anybody aware of any hardware that poser doesn't like? for example my Nvidea G-Force FX5500 graphic card... that is the component that is sending the input to the monitor! Searching the net I have found a few gamers who experience similar problems with nvidea products... I would have thought poser is a lot less demanding on the graphics than most games!.. (I tried turning the acceleration down/off... it didn't chamge anything..)