Imac 2007 unable to restart in recovery mode

That iMac will have left the factory with a set of two grey-labeled DVD discs. These were to be used to reload Mac OS X an the applications that were included with the iMac. They should have followed that iMac to the grave. Without those discs recovery will be difficult. The discs are machine model and year specific and very difficult to find.

That iMac originally shipped with Mac OS X 10.4 Tiger.

The Mac OS X Recovery partition wasn't introduced until 10.7 Lion was released in 2011.

If that iMac was never upgraded to 10.7 Lion or newer, then it has no Recovery partition and cannot boot to Recovery mode.

An alternative would be to find an original 10.6.3 Snow Leopard full retail dvd (white label with the cat) and use that to reinstall 10.6.3, then track down a Mac OS Lion installer.

Target Disk mode might be worth looking into to gain access to the drive from another Mac so that you can wipe and reload an OS.

Transfer files between two Mac computers using target disk mode - Apple Support

+1 to rkaufmann87's posted info above.

Unless you have the original DVDs that shipped with it, then your best option is to return it as it cannot be restarted without the password and if there is no recovery partition then you cannot do anything with it at all. It is NEVER a good idea to buy a used Mac unless you are buying an Apple Refurbished Mac or a used Mac from a reputable reseller such as Macsales.com. NEVER EVER buy from places such as:

• Local Thrift Store
• Ebay
• Craigslist
• MarketPlace
• Local Computer shop
• Your best friend

Why, because in most cases you have absolutely no idea what you are buying and most of these machines were never set for resale per Apple's directions in What to do before you sell, give away, or trade in your Mac.

Best of luck and if you cannot return the computer then please at least recycle it using Apple's free recycling. You can take it to any Apple Store or you can use Apple Recycling Programs which is also free.