@redwave first, here is the [https://download.lenovo.com/consumer/desktop_pub/ideacentre_horizon_27_hmm_20130427.pdf|maintenance manual] for your computer. Hang onto it since we may need it. You are not telling us if you can get into the BIOS and/or which version Windows you are using. Since you already replaced pretty much everything, I would look into the hard drive being the culprit. Press and hold the F1 key then turn on the computer. When the Lenovo BIOS Setup Utility program is displayed, release the F1 key. See if your computer "sees" your hard drive. You also want to try to set the boot order by selecting a startup device. Get a bootable USB drive or similar and see if that gets it to start up properly.
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@redwave first, here is the [link|https://download.lenovo.com/consumer/desktop_pub/ideacentre_horizon_27_hmm_20130427.pdf|maintenance manual] for your computer. Hang onto it since we may need it. You are not telling us if you can get into the BIOS and/or which version Windows you are using. Since you already replaced pretty much everything, I would look into the hard drive being the culprit. Press and hold the F1 key then turn on the computer. When the Lenovo BIOS Setup Utility program is displayed, release the F1 key. See if your computer "sees" your hard drive. You also want to try to set the boot order by selecting a startup device. Get a bootable USB drive or similar and see if that gets it to start up properly.
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Alos, not sure about resetting the CMOS battery. I would suggest a new one.
@redwave first, here is the [https://download.lenovo.com/consumer/desktop_pub/ideacentre_horizon_27_hmm_20130427.pdf|maintenance manual] for your computer. Hang onto it since we may need it. You are not telling us if you can get into the BIOS and/or which version Windows you are using. Since you already replaced pretty much everything, I would look into the hard drive being the culprit. Press and hold the F1 key then turn on the computer. When the Lenovo BIOS Setup Utility program is displayed, release the F1 key. See if your computer "sees" your hard drive. You also want to try to set the boot order by selecting a startup device. Get a bootable USB drive or similar and see if that gets it to start up properly.