Generally even if you uninstall XAMPP, better delete the XAMPP folder before installing any other XAMPP.
If it is a new install, delete the database and re-create it anew and delete the contents of the frontaccounting folder as well before unzipping the contents of FA 2.4.9 afresh and make sure you have the post release fixes as well from the 4th post in the release thread to overwrite their counterparts in the release.
If, however, you had data in FA v2.4.8 and upgraded by unzipping the FA 2.4.9 into it or used the change files set in the 3rd post in the release thread, then use the 4th post in the release thread to update to current state and you will be good to go.
Otherwise, if you upgraded from some earlier version prior to getting it into FA 2.4.8 itself, then you should follow instructions in each intervening release thread thereafter before doing the above.
All of this is also dependent on what extensions/languages/themes you additionally installed in each version and tweaks you incorporated each time. Furthermore, there are caveats on which chart of accounts you used for each company in the FA installation and during usage thereafter. Particularly, the order of fields and incorporation of missing settings in each config distribution sample that comes with each FA version that need to have equivalents in the current config.php file and the settings in the sys_prefs table as well in each database that FA companies use.
If it is for a serious production installation, and you are not sufficiently conversant with PHP/MySQL and the basics of webserver based application rollout, please seek professional assistance posting your needs and bounties in the job offers board. There are enough forum users in your country itself and / or those familiar with the local language and laws who are quite knowledgeable and willing to help.
The following are the top posters from your country:
@almohasb
@obahey
@abozeed
@AsimACC
@JavaMan
@AhmedSelim
@Mahmoud Ali
