It usually takes a lot to stop XP in its tracks. Even in those rare cases when the operating system is badly damaged, you'll usually at least have the option of booting into the "Last Known Good" configuration, or to Safe Mode. But sometimes, especially after major hardware failures or part swaps (e.g. moving the operating system to a new hard drive), or after problems with dual- or multi-booting software, you may encounter seemingly intractable errors such as "Missing or corrupt HAL.DLL," "Invalid Boot.Ini," or "Windows could not start..."