XP's Little-Known 'Rebuild' Command

There's an easy fix for "Missing HAL.DLL," "Invalid Boot.Ini," and several other fatal startup errors.Use at your own risk if you have such problems, but it might be something worth jotting down for later on, as I have had to deal with many Windows XP problems where files were missing and I just had to start over with a fresh install.

From the article:
{
For example, if you already have some knowledge of the commands involved, many "Missing or corrupt HAL.DLL," "Invalid Boot.Ini," or "Windows could not start..." problems can be fixed with these five shortcut steps:

* Boot from your XP Setup CD and enter the Recovery Console
* Run "Attrib -H -R -S" on the C:\Boot.ini file
* Delete the C:\Boot.ini file
* Run "Bootcfg /Rebuild"
* Run Fixboot

It really can be as simple as that!
}

Also find the official method to do the same(which is bit tedious) and full details here.