iMac Intel EMC 2390 Will not boot

There's a wide choice of replacement drive'' types and sizes.

Late 2009 and after introduced models use a proprietary "connector that use the drive's internal temperature sensors" rather than an external sensor like earlier 20-Inch and 24-Inch Aluminum iMac models.

This means that the most straightforward way to upgrade the hard drive is to "replace the drive with another model from the same manufacturer that [OWC or another third-party has] confirmed works properly with this thermal sensor cable". OWC provides a list of compatible drives. Readers have shared reports that taping an external temperature sensor to a hard drive or SSD that does not have an internal sensor will work in these models, but this method could be risky when data is important.

Ensure you get a drive is guaranteed to work (some claim backward compatibility but stall or freeze)'' so you do not occur return fees.

If this Answer is helpful please remember to return and mark it Accepted.