The wonderful folks at Apple give away the system files for System 6.0.8 and System 7.0.1. It's not abandonware; it's legal to use on older Macs. You'll probably want to stick with System 6. It will feel quite a bit faster than 7 (at least it does on my 2 SEs). You can download the disk images (US English) from http://download.info.apple.com/Apple_Support_Area/Apple_Software_Updates/English-North_American/Macintosh/System/Older_System/System_6.0.x/ Since a Classic has a 1.4 MB floppy drive, you can download the two 1.4 MB System 6.0.8 disk images.If you only have access to a Windoze machine, you'll have to download Stuffit Expander for Windoze to decompress the archives. Then you can use WinImage or rawrite to write the resulting disk images to floppies. If you're on a Mac, decompress the archives with Stuffit Expander and write the resulting disk images to floppies with Disk Copy. Stick the first install disk in the drive and boot the machine. It will boot from the floppy drive. Use HD SC Setup on the floppy to format the hard drive and use Installer to install new system software.
Official 68kMLA Music and NeXT Expert
OpenStep Page at http://openstep.topcities.com/
Macs Liberated: SE (2), IIsi, Quadra 700, 6100, PB 5300, PowerMac 5400/200, Performa 6400/180
PCs liberated from Windoze: 3