Apple iMac late 2006 Core Duo (Winchmore Hill N21)

Got this today but it gets stuck at boot up and I can't get the OS restore to work so I'm offering back up for someone who knows how to rebuild a mac. Main unit only with original box, keyboard and mouse are needed for another project so are not included.

Please state your experience with Macs and what you want to use it for when you request, as well as when you can collect.