How to erase a 2001 iMac that won't connect to the internet?

A 2001 iMac isn't capable of Snow Leopard; use its original disks instead.

If you meant a 2011 model, restart with the Option key held down; you may be asked for a firmware password. These units will only support the Command and R option if they have Lion or newer installed, or the Internet Recovery system with a firmware update.

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KSGart wrote:

I just want to securely erase it and send it to recycling

if it was me, I would open it up and physically remove the HDD.

please see iMac G3 Hard Drive Replacement for steps to open it up.

KSGart wrote:

... I’m about ready to drill a hole through it and sending to Apple recycling that way!

That's the easiest thing to do, and more secure than any action short of it.

The only improvement would be to drill multiple holes.

Our friend, @Niel, has you covered. 👍🏽

The 2001 iMac shipped with Mac OS and Application reinstall CDs that should have remained with the computer throughout its life. Without them you have few, if any, options today.

Those old iMacs could not boot from external USB drives and they won't recognize any contemporary Mac drive formats.

As vintage hardware they may look cool on display, but have no real productive value as computers go.

KSGart wrote:

I just want to securely erase it and send it to recycling

Then that is much easier to do.

Assuming the internal Hard Drive is still reasonably healthy, you can create a bootable ShredOS USB stick which you can use to write zeroes to the whole physical Hard Drive. You can use just about any recent computer or OS to create the bootable ShredOS USB stick. Just use the downloaded ISO or IMG file as a source for Etcher (Mac, Windows, Linux) which will make the bootable USB stick for you.

Then you will need to Option Boot the Mac by holding the Option key immediately after hearing the startup chime in order to access the Apple boot picker menu where you will select the orange icon labeled "EFI".

You should be able to use the first link for the Vanilla v0.38 64bit IMG file.

Keep in mind that it can take hours or even a day or two depending on how large the Hard Drive is and its health & speed.

Here is a YouTube video showing how to use ShredOS.

https://www.youtube.com/watch?v=3Cl-LtK39rs

Just ignore the Windows section at the beginning of the video and start watching at the 1:40 mark where it shows ShredOS booting (it will look the same on a Mac at that point).....just follow my instructions above to create & boot the ShredOS USB stick. The 1:45 mark is the point where ShredOS has finished booting & is sitting at its main interface. It is a very simple & crude looking interface, but don't be turned off by it....it just allows it to run on just about any compatible computer regardless of system resources & age. The ShredOS session ends at the 3:54 mark. After that they use a Windows PC to review the log file & results......you can just as easily connect that ShredOS USB stick to a Mac to do the same (assuming it was able to save the log).

I would just select the simplest options for ShredOS such as:

• Single pass erase
• Write zeroes, but you can choose the PRMG method they used in the video as well although PRMG may be slower on such an old system.
• Verification Off -- No need for this and it will just take even longer assuming the drive is healthy enough to survive a single pass anyway, but if you want it verified, then I would choose "Verify Last Pass" so that you have the best chance of actually completely erasing the Hard Drive before the drive physically fails in case the drive is not healthy. Verification is a luxury, but getting as much of the Hard Drive erased is the critical thing.

What is your ultimate goal here? Is it to securely erase this iMac for recycling or to sell, or do you wish to reinstall macOS onto for your own use or for someone else?

I just noticed that you identified your Mac as a 2007 model.

for the 20 inch, here's how to remove the Hard Drive.

and for the 24 inch, see how to remove the Hard Drive here.