Logitech mouse won't install

HAVE: iMac G5 with MAC OS X 10.4.3 (8F46) KERNEL VERSION: DARWIN 8.3.0 AND TRYING TO INSTALL A LOGITECH MX700 WIRELESS MOUSE.
TRIED WITH OLDER AND THE LATEST VERSION (1.6) OF LOGITECH'S DRIVER BUT I KEEP GETTING THESE ERRORS:

System extension Cannot be used.
The system extension “/System/Library/Extensions/LogitechUSBIDevices.kext” was installed improperly and cannot be used. Please try reinstalling it, or contact the product’s vendor for an update.

System extension Cannot be used.
The system extension “/System/Library/Extensions/LogitechUSBIDevices 04-05-01.kext” was installed improperly and cannot be used. Please try reinstalling it, or contact the product’s vendor for an update.

I READ IN A FORUM THAT I SHOULD RE-INSTAL THE OS!!
AS A NEW MAC USER I AM A LITTLE LEERY OF DOING THAT.
SUGGESTIONS APPRECIATED.