I have successfully upgraded from Creative Banshee to V5 5500, but now having video playback problems. I have reinstalled Matroska pack, but right when video playback starts, the computer reboots.

Can anyone help?

No error message ?
or a BSD ?

No BSD or error messages, instant reboot.

I have figured it out though. On MPC (Media Player Classic, and other DirectShow players i assume), in the options dialog, playback-output needs to be set to 'system default' rather than 'overlay mixer'. I have done this with the Banshee in the past, but it's been such a long time since i change vid cards that i forget all about it.