How can I find programmatically the installed programs (windos XP)and
their location (folders) Prefereed language "C"

Hi freund,

You can access the list of installed application on Windows XP by
examining
the windows registry at the following location:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\

Each entry under this location has many keys, but the two you're
probably
interested in are "DisplayName" and "InstallLocation". (I include a
link
to a programmatic approach below, but if you wish to examine your
machine
to see get an idea of the structure you can do so by running the
windows
registry editor - type 'regedit' into the Start->Run dialog).

Of course, this will only give you applications that have registered
themselves
upon installation. Some simple applications are installed by simply
unpacking
themselves to your hard drive; these will not show up in the list.

Here's a link to simple batch script that will output the list of
intsalled
applications, useful for testing purposes:

http://www.fpschultze.de/bsh.htm#a18

And here's a tutorial with VB code that show's you how to read list of
installed programs from the registry:

http://www.mvps.org/vbnet/index.html?code/reg/reguninstall.htm

I wasn't able to find any C code for your specific requirements, but
here are some links on how to access the registry using C/C++:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnppc2k/html/ppc_stry.asp

http://www4.ncsu.edu:8030/~jgbishop/codetips/general/registry_access_advanced.html

Also, here's a discussion as to why you can't always trust the 
list found in the registry:

http://www.karenware.com/newsletters/2000/2000-05-29.asp

Basically, some programs don't get removed when they're uninstalled.
This
link includes VB code to prune the registry of dead entries - you
could incorporate some of this code to prune the list you get from
above?

Cheers,

Eadfrith

Apologies for the messed up formatting - I need to stop hitting the
return key at the end of a line! Also, a preview feature would be nice
(hint hint).

Cheers,

Eadrith