I'm betting that you've got AVCHD files. Nasty to edit. I've read that they take heaps of PC resources. Your PC is a 1.6 is that a dual? Anyways, I don't know enough to inform, you but please look into AVCUpShift. It is meant to assist by converting AVCHD files to m2t files. See here: Sony HDV Info .com AVCHD HDR CX7 SR5 SR7 PMW EX1 XDCAM - AVCHD - Mpeg2

Sorry, can't be of any further assist here.

Grazie