Locking or fixing set resolution

Hey again,
I did a search for this topic, and didn't find anyhing
on it.

anyway, sometimes when i am web surfing
or playing a video...
the resolution will switch from 1024x768
to 800x600.

Is there way to "lock" in
1024x678

this is the only resolution i want
(i would like 1400x968, but not available on
current video driver.)