Motherboard not recognising GPU

Until a couple of weeks ago I was quite happily running my Nvidia 9400 GT GPU with no issues. Windows update wanted to update as it does every now an then and afterwards I get a black screen?? I switched to my on-board graphics everything is fine - I try the 9400 and nothing........ it gets weirder....... couple of days later I turn the computer on again and the 9400 is working again..... does so for a few days then black screen again

I've been out today and bought a Nvidia GT 620 and plugged it into the motherboard but even that isn't showing up in device manager.
I'm glad I got the new card in any case although bit gutted I may not have needed it but can someone please help me sort this out its driving me insane!
Has windows update screwed my machine or am I missing something??
Before anyone tells me to plug the vga cable into the 620 and enter safe mode or bios..... I cant as the screen is black. The fan is turning on the card so it has power, my power supply is definitely man enough so please, please, please help me I cant handle my on-board graphics anymore :'(

coldpost said:

Until a couple of weeks ago I was quite happily running my Nvidia 9400 GT GPU with no issues. Windows update wanted to update as it does every now an then and afterwards I get a black screen?? I switched to my on-board graphics everything is fine - I try the 9400 and nothing........ it gets weirder....... couple of days later I turn the computer on again and the 9400 is working again..... does so for a few days then black screen again

I've been out today and bought a Nvidia GT 620 and plugged it into the motherboard but even that isn't showing up in device manager.
I'm glad I got the new card in any case although bit gutted I may not have needed it but can someone please help me sort this out its driving me insane!
Has windows update screwed my machine or am I missing something??
Before anyone tells me to plug the vga cable into the 620 and enter safe mode or bios..... I cant as the screen is black. The fan is turning on the card so it has power, my power supply is definitely man enough so please, please, please help me I cant handle my on-board graphics anymore :'(

Not the clearest post.

You can run the system using the onboard graphics? If so, I suggest the following:

Have the latest drivers on hand for both your onboard and the GT620.

Uninstall your graphics drivers.

Shut down. (Don't reboot.)

Install the GT620. Plug the monitor cable into it.

Power up. If you get the POST (power on startup) display, things are probably OK. If not, perhaps you have a hardware problem.

If you can get into Windows with the new card, install the new drivers. With any luck, Bob's your uncle.

I upgraded from a 8800GT to GTX 560, weeks ago installed card run fine for about 2 hours the black screen, monitor still on, windows loads, still black screen, then 3 days later bingo monitor works again! weird. Never found out why though.