The 7.5.3 files from Apple can be burned to a CD on a Windows machine, but to install it you will need to have a boot disk or working OS on the Mac, as the CD you make won't be bootable. You can download OS 7.6 or OS 8.0/8.1 off the web and burn them using Windows (as long as it's a standard CD format like ISO) though. You'll need at least 12 MB of Ram for OS 8 to install though - without a working OS on the machine it's not so easy to find out how much you have until you have got your OS installation CD and can boot it up with that. The 610 has 4 MB of Ram built in, so if you look inside and there are no additional memory modules installed then you only have 4 MB, and if there are modules in there then they may or may not have some indication of their size on them.