Codecs?

Has anyone experienced problems with conflicting codecs? Is this
possible?

I have had my PC (Athlon 64 3800+ with Asus MB) for about 4 months and
have loaded up various video editing/DVD authoring packages (Pinnacle
Studio, Womble, Nero 7.xx, WinAVi etc) and the Storm Codec pack.

I have had problems as follows:

1) In Windows Explorer, when you right click on any video file the
screen blanks for a couple of seconds and then comes back again.
2) When I change Windows accounts the screen goes blank before logging
into the other account.
3) The PC suddenly powers off - totally. This has happened usually when
it is not being used - I have been in the room when it happens, there
is no warning, it just powers off.

Event log shows nothing - anyone know something better that can log all
sorts of info about the PC.

I have had the PC back to the store where I bought it and their tests
could find no problems, but I did make them replace the power supply.
The tech suggested I might have conflicting drivers (are codecs drivers
of a sort, since you can view them in device manager).

Any thoughts?

Thanks,

Paul