boot stuck on black screen with cursor pointer

I have recently upgraded from Windows XP to Vista and everything was working fine. Then one day, one of my little cousin resetted the computer and after that Vista will not boot at all. It will normally boot with the microsoft logo but will not go further where we see the Vista green screen. After that it gets stucked on a black screen with only mouse cursor showing on the monitor. I even tried to boot in safe mode and also tried to repaid it but that didnt help. I tried to reinstall from the Vista DVD as well, but it wont pass the product key screen. So, is there anyone who can sort this problem for me. Thanks

The problem that you are facing may occur in many scenarios. These scenarios include the following:

1. The registry is corrupted.
2. A System file is missing or damaged.
3. A device driver file is missing or damaged.

To resolve this problem, use the Startup Repair tool. The Startup Repair tool can fix some problems that prevent the operating system from starting correctly. More information here - http://support.microsoft.com/kb/925810/en-us

You can try to start the System Restore tool by using the safe mode option with the Command prompt in Windows Vista:

1. Restart your computer, and then press and hold F8 during the initial startup to start your computer in safe mode with a Command prompt.
2. Use the arrow keys to select the Safe mode with a Command prompt option.
3. If you are prompted to select an operating system, use the arrow keys to select the appropriate operating system for your computer, and then press ENTER.
4. Log on as an administrator or with an account that has administrator credentials.
5. At the command prompt, type %systemroot%\system32\restore\rstrui.exe, and then press ENTER.
6. Follow the instructions that appear on the screen to restore your computer to a functional state.

Try to use the Bootrec.exe tool in the Windows Recovery Environment to troubleshoot and repair startup issues in Windows and see if that helps. To run the Bootrec.exe tool, you must start Windows RE. To do this, follow these steps:

1. Put the Windows Vista installation disc in the disc drive, and then start the computer.
2. Press a key when you are prompted.
3. Select a language, a time, a currency, a keyboard or an input method, and then click Next.
4. Click Repair your computer.
5. Click the operating system that you want to repair, and then click Next.
6. In the System Recovery Options dialog box, click Command Prompt.
7. Type Bootrec.exe, and then press ENTER.

It could be that the Windows Boot Configuration Data file is missing required information. This error occurs when either of the following conditions is true:

1. The Windows Boot Manager (Bootmgr) entry is not present in the Boot Configuration Data (BCD) store.
2. The Boot\BCD file on the active partition is damaged or missing.

So to resolve this problem, you can follow the method given here - http://support.microsoft.com/kb/927391/en-us