How can I know what are the original files of an Acer Aspire One? I want to delete all files that didn't come with it originally.
The most reliable way to do this is to insert any "factory restore disk" that came with the computer (hopefully you have this, otherwise Acer can probably send you a replacement in the mail if you phone their technical support if the model isn't too old) and just restore it to its new state (which will effectively wipe out everything and leave you with just the original files).
Reboot the system and when you see the Acer logo, press Alt+F10 (also try Alt+F11). That will load the restore tool from the backup partition which allows you to reset the system to the factory defaults.