Stop 0x0000007B or INACCESSIBLE_BOOT_DEVICE
Causes : The Stop 0x7B message indicates that Windows XP Professional has lost access to the system partition or boot volume during the startup process.
Solution :
Run any system diagnostics that are supplied by your computer manufacturer, especially a HDD check.
Rebuild the Boot.ini file.
Run chkdsk /r or chkdsk /f to detect and resolve any file system structural damage.
If all Hardware fully functional reinstall Operating System.