Hi,
The HP ProLiant ML110 G5 Server was retired on June 30, 2010, which means that future release of operating systems would not be tested from that date for compatiblity and drivers be released. Now, Windows Server 2012 was released much later than the release date.
Having said that, it does not mean that it would not be possible to install or work, but just that drivers and other applications are not developed by HP for this version of operating system. This server supports Windows 2008. Hope this helps!
Regards,
Vijayasarathy