Copying program files is not the same thing as installing a program, so most
programs won't work properly when copied in this way.
The reason is that when a program is installed, it typically creates both
files and registry entries, and sometimes takes other actions. You need to
use the installation program that came with the program to install it
properly. Also, an installation will often put files in folders other than
C:\Program Files, especially C:\Windows\system32, that you did not copy.
For future reference, Windows Easy Transfer can help you transfer data files
and some other things:
http://www.microsoft.com/windows/products/windowsvista/features/details/easytransfer.mspx
However, it will not transfer programs. Microsoft is beta-testing a similar
feature that will also transfer programs, but it will likely only work with
programs that install themselves in a standardized way so that it can keep
track of which files and registry entries it needs to copy over. Old
applications will not be able to be transferred.
The bottom line is that the only way to guarantee that a program works
properly when transferred it to install it using its installation program.
Paul