T430, disable "OS Detection for NVIDIA OPtimus" in BIOS, no graphic card can be found in Windows

Question

I try to use my T430 minidisplayport to connect with external display. But it is so unstable that the connection between laptop and display can lost anytime. That is so annoying. I use Nvidia control panel in Windows to force use NVS5400M instead of HD4000, but it seems doesn't change anything.
I heard if I select the discrete graphic card in BIOS, then it may fix the display connection lost problem. Then I go to the BIOS and  set the "discrete", and disable "OS Detection for NVIDIA OPtimus" in BIOS Config Display (This is necessary otherwise the laptop will change it back to Optimus automatically.). But after I log into Windows, then no graphic card can be found, Why? How should I fix this problem?
The external display issue in T430 is so annoying. The VGA suffers very serious noise while the minidisplay is so unstable. Even worse, there is no any lenovo staff stand out to help !!!!!!!!!!!!!!
If anyone has experience, please share that.
Thank so much.

Answer 1

Hello Mark, thanks for help. Please see my answers below:
1. Windows 7 Ultimate 64 bits.
2. Yes, I did. The BIOS is latest (2.65). The NVS5400M driver is 333.02.
3. My display is Asus MX239, which only has HDMI. I use an adapter cable: miniDP->HDMI and then an HDMI-HDMI cable I try to connect to a Samsung TV, but similar. I don't have a miniDP to HDMI cable. I just order one but has not get it.
Sorry that I post in multiple threads. As I mentioned in that thread, let me conclude all these here.
After I disable "OS Detection for NVIDIA OPtimus" in BIOS, then I istalled the NVS5400M 333.11 driver. Then the NVS5400 can be found in Windows. But the displayport problem still exist. It is still very very difficult to detect external monitor (this means in most cases I can't switch to external display), and even sometimes it works, the connection can lost anytime.
Even worse, I found a new problem, that if I disconnect my T430 with power supply, then I can see the "pink bar" appear and disappear in the laptop screen (not external monitor) repetitively, quickly. I have never seen this problem before, only after I install NVS 333.11. Then I reinstall the 333.02 driver. Then I enabled the "OS Detection for NVIDIA OPtimus" in BIOS again. The "pink bar" issue gone. It looks like the issue is caused by 333.11 driver. But this driver comes from Nvidia offical driver download website.
So now the most important thing I need help is, I need to have a stable solution to connect external display. In T430, there are only two ports for external display:
1. VGA
2. MiniDisplayPort
Please help me following questions:
1. When I try to use VGA, I can see very very bad noise in external display. This issue also be posted in previous thread in forum. This should be a hardware design failure. Is there any solution to fix this that I can use VGA without noise in external display?
2. My T430 has both HD4000 and NVS5400M, if I need to use miniDP (which is I prefer, I have digital port why I use VGA.) for display. Does miniDP only work when the NVS5400 is used (it looks like that)?
3. If miniDP only works NVS5400, so how should I configure to ensure the T430 use NVS5400 all the time? Do I have to disable "OS Detection for NVIDIA OPtimus" in BIOS or I can switch using Nvidia Control panel in windows ?
4. Would you please provide me a configuration for T430 (include BIOS, and setting in Nvidia Control panel) that can support stable external display thru miniDP? Include driver versions and BIOS version.
5. What are potential reasons that the external display can't be detected and can lost connection anytime with T430? To be noted, I already set to use NVS5400 in Nvidia Control panel. The case is also same I disable "OS Detection for NVIDIA OPtimus" in BIOS. I think cable may be a issue.
Thanks again.