1) add your langauge folder in lang folder
2) edit  installed_languages.inc to add new language as Example :
---------------------
$installed_languages = array (
  0 =>
  array (
    'code' => 'C',
    'name' => 'English',
    'encoding' => 'iso-8859-1',
  ),
  1 =>
  array (
    'code' => 'ar_EG',
    'name' => 'Arabic',
    'package' => 'ar_EG',
    'encoding' => 'utf-8',
    'version' => '',
    'rtl'     => 'right-to-left',
    'path' => 'install\lang',
  ),
);

$dflt_lang = 'C';
?>
--------------

the same  for modules and so on >>>
I hope i help someone for this issue

Fatal error: Maximum execution time of 60 seconds exceeded in C:\xampp\htdocs\akunting\includes\session.inc on line 28

Below are lines 27 and 28 of session.inc:

// Make sure the session hasn't expired, and destroy it if it has
if ($this->validateSession()) 

I have experimented changing the max_execution_time from 60 to 120 and even 600, but it didn't help. The error persists.

What happened on browser?

The server this is installed on is a Window 2003 Server.

Beware of case sensitivity and all paths are relative to the FA folder in the webroot.

This is probably specific to Win7 installs.

I believe it is a permission issue as well, but it is one that can crash a web server. That, to me, elevates the issue to something we should note for future installs. In my case I have set up a demo server to show off the product to accounting. The first thing i did was to check the installs to see what check writing tools were available and this issues showed itself.

Also can you be more clear as to where this and that should be. You stated that i should copy over the empty.po to c.po. Do you mean rename it c.po? Where is this file located? I found empty.po in the FAroot/lang/new_language_template/LC_Messages - but the error log shows a ../lang/C/LC_messages directory that does not exist.

It is most certainly a permissions issue on the folders.

Which versions of XAMPP / Uniform server are you using?

I am getting the exact same error. OpenSSL is open and working. The Diagnostics page reports no errors. I started using a Windows 7 machine and just installed Xampp server and ran FrontAccounting through xampp's defaults. Everytime i clicked on any of the install links it would crash apache. Xampp would restart the service. I noticed other users stated they used a different computer so i formated the machine i was using and installed Windows 2003 server as another attempt. I setup xampp again and i still received the same problem and apache is crashed and restarted in the process. In fact the xampp install shows multiple ports (main 2 show as 80 and 443). When you click on the install links a bunch of 1000-1300 ports are accessed (i can only assume OpenSSL) while ports 80 and 443 are either dropped or not shown. I decided to see if xampp is the problem so i deleted the entire xampp and installed Uniform Server. Uniform server's default settings are set for openssl as on for the default. FrontAccounting install listed no problems. On this install Uniform Server does not show any errors, but it performs the same actions when clicking on any of the install links. I don't seem to lose apache server, but either way i cant use this software if I click a link and it thrashes my webserver. I understand that it could be settings, but this is the equivalent and a self destruct button because FA doesn't get what it's looking for or my webserver doesn't understand it.
The only errors appearing in the log file are listed below. I attempted to see if the PEAR directory was a problem and changed various links within the xampp settings, but in the end nothing worked. This is very frustrating as I was going to demo the software, but the errors make it unusable in any enviroment. I am at a point where i will dump FA if i cannot fix this issue. I really would like to give it a try and support the community, so if you have any ideas on where to start, please send them my way.
ERROR FILE LISTED BELOW:
[19-Nov-2012 17:27:04 Europe/London] 0::session.inc:369: include_once(./faillog.php): failed to open stream: No such file or directory
[19-Nov-2012 17:27:04 Europe/London] 0::session.inc:369: include_once(): Failed opening './faillog.php' for inclusion (include_path='.;C:/UniServer/home/us_pear/PEAR')
[19-Nov-2012 17:27:04 Europe/London] 4 Domain file "./lang/C/LC_MESSAGES/C.po" not found.
[19-Nov-2012 17:27:12 Europe/London] 0::session.inc:369: include_once(./faillog.php): failed to open stream: No such file or directory
[19-Nov-2012 17:27:12 Europe/London] 0::session.inc:369: include_once(): Failed opening './faillog.php' for inclusion (include_path='.;C:/UniServer/home/us_pear/PEAR')
[19-Nov-2012 17:27:12 Europe/London] 4 Domain file "./lang/C/LC_MESSAGES/C.po" not found.

I have the same problem, I think this problem is only on windows machine

I've installed FA 2.3.11 on Windows 7 machine running Apache and MySql. Installation without any error, running perfectly fine, no problem at all. Only problem is none of the following options are working under Setup/Maintenance
  Create/Update Companies
  Install/Update Languages
  Install/Activate Extensions
  Install/Activate Themes
  Install/Activate Chart of Accounts

When I click any of the above option I get error:
Error 101 (net::ERR_CONNECTION_RESET): The connection was reset.

I don't know the reason as everything else is working perfectly fine, except for above.
I am able to access internet from the browser and I am logged in as admin.

Does this require any changes in Apache MOD etc...

Please help me

It is something in XAMPP default configuration. I switched to "uniform server" and now every thing works fine. It seems uniform server is more compatible with windows.

Regards
Kelile

/Joe