HDD Not mounting/Not visible

iMac late 2009 21,5' - intel code 2duo

Osx 10.9.5

HDD 1tb vertabrim

So I have had this mac for 4 years, the HDD the same.

Today rendering a 10min video project, to the end I decide to open chrome, and other apps...

my mac freezes (I think nearly never this has happened)

hard restart, but my HDD does not appear

this sometimes happens with a rare kernel panic, you just restart and the HDD appears or tun off on usb

this time, no restarts, turning off for 15min, disconnecting does not work

it also does not appear un disc utility, or in other accounts

but yes in a windows pc..!