It is important to note that the reason why you cannot simply move application and Windows files is because moving them does not update the Registry with new locations.
That said, moving most applications can be done without a complete reinstall (I don't recommend moving OS files).
If you have Microsoft Office, for example, you can move (cut and paste) the folder. Then run install and tell the routine to install in the new location. The install program will see Office is there, and prompt to "fix" it. Say yes, and it will update the Registry for the new locations, without losing all your customizations.
Again, don't try this with the OS files - just the programs you installed.