Stuck at "starting windows" screen

[joneexp]

Hello , as the title says, when I start my computer it freezes/get stuck in "Satrting Windows" screen.
1st time I got this problem I took out RAMs and I put them back in and I ran a memtest and it gave no errors , then started the computer and it worked fine.
This time I tried :

• 
  - Safe mode with all its types. Safe mode also freezes at classpnp.sys
  - Last know good configuration. this doesn't solve anything.
  - F8 => Repair computer. this gets stuck in green loading bar with "Microsoft corporations" Screen.
  - I inserted the original CD that I installed windows 7 from and tried to access System recovery options through repairing and it gives me an error that says This version isn't compatible.
  - I booted with memtest and ran tests on RAM aswell it gave no errors.

but still nothing , what else can I do to solve this problem please ?!

My computer is HP Z400 Workstation , Intel Xeon CPU , 4gb RAM , 2 weeks and half ago I installed a nvidia geforce 210.

 

[gregrocker]

Work through the steps for Troubleshooting Windows 7 Failure to Start which try everything possible for starting the OS, leading up to if necessary rescuiing your files to Performing an HP system recovery or do the superior Clean Reinstall Windows 7.

Even if you choose to do the HP recovery be sure to read the Special Note to HP Owners at the end of the Reinstall tutorial as it will explain about Minimal Recovery available on many models that is almost as good as a Clean Reinstall.