l Lenovo Thinkpad T60, Type 2007-ED9 (WinXP, SP3; 1G RAM; ATI Mobility Radeon X1300)
l External monitor (Samsung Syncmaster 2494) - using D-sub cables that came with the monitor and plug into the side of the computer.
It worked well before, it automatically started up with the external monitor as the primary screen and the laptop's screen as the secondary - something I didn't like and tried to change, and the problem seemingly began there. I went to Display -> settings to make the thinkpad's lcd as the primary (I am pretty sure that's all I did), which it did, but the external monitor, though still connected, went blank. The computer still detects it, as the screen's model and native resolution shows up on the display settings. The screen itself is just blank, it doesn't show the message that it's looking for a signal, but it does occassional has alternating "Digital" and "Analog" boxes showing for a few seconds (as if it's trying to determine the source of input), and then it is blank, as it otherwise just does.
The monitor and its cable are working well, because extending the desktop onto it with another laptop worked fine.
WHAT HAD BEEN TRIED
Installing again Syncmaster 2494 drivers both the analog and digital ones;
Play with the Display-settings both from the desktop and within the ATI Control Centre to make it extend. The Syncmaster is blanked out the whole time (as above), but still the computer detects and the monitor doesn't show "No Signal Detected" message. And actually my mouse goes off the primary Thinkpad LCD into the blank screen, just that I can't see it.
Fn+F7 to bring up the presentation manager to toggle between display modes... the computer will try to extend onto the Syncmaster for 5 seconds (which I noted as the icons on my desktop on the Thinkpad LCD disappeared for that duration), whilst the screen stays blanks, and then it gives up and everything on the desktop reappear back on my Thinkpad LCD. And no improvement in situation.
Unplugging the monitor from the jack and turning it back on; including switching the ends of the cable (using the plug to the monitor to plug into the laptop).
Reinstalling WinXP from scratch to get rid of whatever I could not undo in Display Settings. During installation. I had the Syncmaster plugged in the whole time. While it stayed mostly blank, on the several reboots during the installation process when it shows message that Windows is going into Rescue and Recovery to do things, I see the message cloned on the Syncmaster. But after all of that. Same situation as before.
Trying a different monitor (LG L206WH Flatron) - after I extended the desktop to the external, it showed up, but in dimmed colors and it only showed on 1/2 of the screen. And it was blinking on and off every few seconds.
I am at a loss as to what is the problem. I don't have a dock, and I only have the cables and ports that came with the basic monitor and laptop. If you could think of something, it'd be very much appreciated!