Just crippled iMac 4.1 with download

[RgrF]

I prefer rollerball so when the ancient Logitech that worked for years gave out I bought a new wifi Logitech. It worked on plug in but when I went to the site and downloaded software, it killed my Intel 4.1 iMac.

Can't start OS 10.6. Tried Disk Warrior using Command "C", nothing. I'm backed up on a cloud (teach me), no original install disks. Appointment at Genius Bar tomorrow AM.

Suggestions?