I get black screen after booting windows 7 before login

Hi, all
I thought this is the correct place to ask this question. I upgraded my system with intel DG41 board and 8GB of ram, and it works fine...

only somtimes when I boot into windows, after the booting screen, just I see a blank black screen, no task manager and explorer too,
I tried different drivers for my nvidia 9500gt, and still same problem, and when i shutdown (holding the power button), and restart, then it works, it log in to windows normally

can anyone help, please

See if these links can provide you with the information you seek.

Why is my screen black when I start Windows 7?

Windows 7 Black Screens of Death for Some AMD/ATI GPUs - Softpedia

windows 7 black screen after login, no desktop show up

[SOLVED] Windows 7 Loads to a black screen. Whats the - Microsoft Answers

Windows 7 won't boot after welcome screen. - Microsoft Answers

Thanks for the information, highly appreciated... I did format the PC and download and installed drivers and now its ok,
though only one problem exist there, i put 8GB of ram and its showing in the configs, but my system runs slower than ever, when i remove one 4GB, then my pc runs normally, photoshop and all the applications work file.. why it is like this?

Re adding RAM
Ram comes in various brands, voltages, and timings.
You want to be sure you match those specification if you desire to keep the same type of memory you have.
It is said that the speed of memory you put in your PC is important because putting a slower speed stick of memory in your PC will cause all of your memory to run at that slower speed.
{I have never added RAM thus no experience here}

Links FYI.

How to get more RAM: Add more memory to your computer

Optimize Windows 7

Optimize Windows 7 for better performance

Optimize performance | Photoshop CS4, CS5

thanks for the reply, its both same RAM, i mean identical, i bought as a pack

thanks for your real help

many wishes

You are most welcome.
Thank you too.