how do i delete all files to donate imac

This support article should help:

What to do before selling or giving away your Mac - Apple Support

Best of luck,

GB

Click here and follow the instructions. If the computer originally shipped with Mac OS X 10.6.8 or earlier, when you reach step 5, insert its original disk, restart with the C or Option key held down, use the Disk Utility to erase the internal drive, and install a fresh OS.

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If your computer shipped with 10.6.8 or earlier and wasn't upgraded to use Apple's Internet Recovery system, you'll need a Mac OS X install DVD.

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No. You can't sell that computer with an OS newer than 10.6.8 on it(or 10.7.5 if you bought one of Apple's Lion installer thumbdrives.)

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Yes it does, because the later upgrades are tied to your App Store Account.

You need to take it back to the original OS X that it came with (plus provide the original disc set) before selling or donating it.

Optionally you could also sell or donate it with a 10.6 Snow Leopard upgrade, but you must provide the Retail 10.6 upgrade DVD.

aerpac wrote:

I dont have the disk utility it's been 8 years, can I still do it without it?

You can get replacement System Install & Restore CD/DVDs from Apple's Customer Support - in the US, (800) 767-2775 - for a nominal S&H fee. You'll need to have the model and/or serial number of your Mac available.

If you're not in the US, you may need to go through the regional Apple Store that serves your location to find the contact number. Here's a list of links to all of those - http://store.apple.com/Catalog/US/Images/intlstoreroutingpage.html Another resource: International Support Phone #s.