On Wed, 17 Sep 2008 22:51:36 +0100, "Avelino Tavares"
wrote:

I turn on my pc, he works ok, but passed some seconds, the monitor start
blink and dont show image.
The computer is still running, but i dont see anything, i make ALT+F4 and
ALT+D and he turns off. What could be ?
I have changed graphic card and memory, formated the pc, but the problem
continues.

You could have some video-mode selected that your monitor does
not support or you have hardware support for more than 1 monitor
with only a single monitor attached. (E.g. both a video card and
on-board video support.)
In the latter case: go into the BIOS setup and make sure that the
proper monitor is selected.

Without dual video support:
When windows is booting, press F8 and select safe mode.
In safe mode, select an unused spot on your desktop, press the
right mouse button and look under Properties - Settings.
Make sure that the resolution (e.g. 1024 x 768) is not higher
than your monitor supports.
Under Advanced - Monitor make sure that the refresh rate is low
enough. (When in doubt: select 60 Hz and see if your PC boots
normally.)

Keep in mind that a CRT monitor that is aging may stop supporting
it's highest resolution and/or refresh rate. A clear indication
for immanent replacement :-)

--
Kind regards,
Gerard Bok