Windows 7: windows 7 startup issue with black screen

i am was installing drivers on my laptop(sony vaio windows7 ulitmate 32 bit) and in between the installation,the system display a message to restart the computer to complete the installation.i clicked the restart button and after it displays a message windows failed to start. a recent hardware or software change might be caused.i tried to repair it by launch startup repair but i see black screen with cursor.i also clicked on starts windows normally,but after windows 7 logo the computer restarts again with some kind of error.i tried to start my computer with safe mode but it loads some deivers and after sometime it stops and show some kind of error and my computer restarts again.i tried to boot my computer but when i tried to boot my computer,the windows logo shows and after that windows loading files and after that i saw again black screen with cursor.i don't know how to start my computer.i have no external device attached.i also clicked on windows memory diagnostic tool but still couldn't find the problem.plz help.........

Hello hadi and welcome to Seven Forums.

I'd try running Startup Repair using this tutorial. Run it 3 times rebooting after each scan.

Startup Repair

If this doesn't fix things I'd try the other suggestions in the troubleshooting guide prepared by one of our Forum experts.

Troubleshooting Windows 7 Failure to Boot