HELLO, I NEED THE DRIVER FOR MY IRIVER IFP-790 MP3 PLAYER. CAN YOU PLEASE HELP? THANK YOU IN ADVANCE. MEIRO

I think you mean that you need the driver for your Computer to recognize the player instead of the iRiver needing an actual driver or firmware. If this is the case, then the best solution would be to google the make and model of your computer and "usb drivers". You will likely find a downloadable .exe driver and that should fix your problem
If that isn't what you mean to say then:
http://www.techspot.com/drivers/driver/file/information/2780/
Heres a link to the latest firmware for your mp3 player.
Just download the .hex file and put it into the "root" folder of your iriver mp3player. Then safely disconnect the mp3 player from the computer. Then go to the general options menus and select firmware upgrade. This should take you through the process of upgrading your firmware.