Want to move a Windows XP Installation to Different Hardware. How to do that ?

In most of the scenarios (legal !), You would be doing one of the following acts:

A. Migrate a working Windows XP operating system and your installed programs to a different or more powerful computer in minimal downtime.
B. Replace a small system/boot disk drive with a larger system/boot disk drive.
C. Restore a Windows backup from a malfunctioning computer to a different computer for disaster recovery purposes

Windows Backup (Ntbackup.exe) can handle differences in hardware configuration information between computers and maintain critical registry entries that are unique to the computer to which You are migrating information. This capability means that You can migrate to new hardware by performing a full backup of the source computer and Then restoring the backup over a fresh installation of Windows XP on the destination computer.

Ntbackup.exe handles restore operations in the registry by first querying the following registry key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\BackupRestore\KeysNotToRestore
This registry key indicates to Ntbackup.exe that certain registry keys under the HKEY_LOCAL_MACHINE\SYSTEM key should not be overwritten when files are restored.

An entry that ends with a backslash (\) indicates that a key is protected and that any keys or values under that key should not be restored. If the entry ends with a backslash and an asterisk (\*), all subkeys are "merged." In this situation, "merged" means comparing the start values of the keys in the backup set with the start values that exist in the current registry, to determine the correct key to restore.

If the value of the key on the backup set has a lower start value, the backup key takes precedence. If the value of the key in the current registry has a lower start value, the current key takes precedence. This process ensures that all services and devices start correctly after a "system state" restoration, even on dissimilar hardware.

Complete details on this are available at Microsoft site at How to Move a Windows XP Installation to Different Hardware (Q314070)