Unmountable_boot_volume?

You will need the operating system install disk.

Restart the machine and on the screen it will say "Press ? to enter setup".? could be F1,F2,Del or another key.

Enter Setup/BIOS.

Load fail safe and defaults.

Set fitst boot device to CD/DVD rom in BIOS/Setup pop in the install disk and save and exit.

You will be prpmpted to press any key to boot from CD/DVD then press any key.

Boot into recovery console with command prompt.

Ok just follow:

To repair the volume, follow these steps:

Start your computer by inserting the Windows startup disks or the Windows installation disk if your computer can start from the CD drive.

When the Welcome to Setup screen appears, press R to select the repair option.

If you have a dual-boot or multiple-boot computer, select the Windows installation that you want to access from the Recovery Console.

Type the administrator password when you are prompted to do this.

Note If no administrator password exists, press ENTER.

At the command prompt, on the drive where Windows is installed, type chkdsk /r, and then press ENTER.

At the command prompt, type exit, and then press ENTER to restart your computer.

After you repair the volume, check your hardware to isolate the cause of the file system damage.

If this procedure does not work, repeat it, but type fixboot instead of chkdsk /r and At the command prompt, on the drive where Windows is installed, type chkdsk /r, and then press ENTER.

At the command prompt, type exit, and then press ENTER to restart your computer.

After you repair the volume, check your hardware to isolate the cause of the file system damage.

If you use a wireless mouse please switch to PS/2 mouse.

I hope this helps?

JB.

Sounds like some critical files used for booting up are corrupted,see if you can run a system restore or last known configuration that worked,if not you might have to reformat and reinstall your operating system so you will lose all your data,sorry! Good Luck!