Bios version 603 covers all previous versions: http://www.asus.com/Motherboards/AMD_AM2Plus/M2N68AM/#
download page for bios file and flash utility program. If the flash utility program won't work with your windows version, write asus tech support for "ez flash 2". I was unable to locate a link on asus website. Before flashing, disable any boot block settings in the bios and windows firewall in the control panel. You may be able to save your old bios file with a usb boot drive or floppy; once the flash program starts, don't touch anything on your system unless it fails to start. Let the program finish, and it will reboot when done or ask you to.