code-red I don't use XAMPP, so the best I can do is do the research for you, and come back with my findings.
php.ini is a configuration file. That means it has a list of options written in it. You can edit php.ini with a text editor, and enable and disable options in it by adding or removing a ; at the beginning of each line.
On Windows, to enable the fileinfo extension, you will need to find a line that mentions "php_fileinfo.dll" and make sure that line is enabled. That means it shouldn't have a ; at the beginning of that line. I don't know if this step is similar on Linux,, but I imagine it would be.
Once you have enabled the missing fileinfo extension, you can restart XAMPP, and it will hopefully be working. If it still isn't working, then you will have another, different, error throw up, and you will be able to fix that, and keep going until it's all done.
I hope that helps. I can't help any more as I've never used XAMPP.
