How to get to the Disk Utility to repair disk errors while necessarily booting from the installation disk 1 ?

Situation: Trusty (so far) 27 inch iMac (Late 2009) running Snow Leopard MacOS X 10.6.8

iMac was no longer booting up, after I couldn’t repair disk errors … First Aid was greyed out.

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Powered up the mac, sliding in the installation disk 1, and holding the option key, The HD icon and Disk icon appeared briefly, but the screen immediately went black.

Tried again…with installation disk still in:

Quickly used the arrow keys to select the install disc to boot from.

Mac booted up to a white screen with a series of grey dots (like big disjointed letters or numbers making no sense) and a full width grey rectangular-like section across the bottom.

Couldn’t seem to do anything of value, yet the mouse moved the cursor across the screen and pressing the keyboard brightened the screen if it dimmed.

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Left installation disk 1 in to boot up from & shut down

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With installation disk 1 still in : experimented:

✽ Tried starting up in safe mode using the shift key = started up to a  blue screen.

✽ Tried starting up in Recovery … using Command + R.  = started up to a blue screen

✽.Tried starting up normally (not holding any keys )  Started up to blue screen…

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As am using installation disk 1 to boot up from: 

No help from: If your Mac starts up to a blank screen - Apple Support. etc.

Would love some help with:

How to get to the Disk Utility screen to repair disk errors while necessarily booting from the installation disk 1 ?

Thank you for reading this, and thank you in advance for any ideas, suggestions, comments.