Late 2009 27'' imac - mini displayport to pc HDMI

Hi,

I was wondering if anyoune could help me.

I have read lot's of forums about being able to use the 27'' imac as an external monitor for other computers (macs, pc's etc). I've also read that you can do this either via the mini-displayport (mDP) to mDP or from mDP to hdmi.

As my pc laptop doesn't have mDP, I have bought an adaptor which goes from the imac mDP to my pc's hdmi port. I was told by apple support that this was a viable option.

However i'm having trouble getting the imac to recognise the connection between the two.

I've been to system preferences and displays and there's nothing there (other than resolution options), and i've pressed command + F2 or fn + command + F2 and nothing happens. I've also restarted both and nothing happens.

Has anyone had any success doing this?

If so, what am i doing wrong; any adice would be greatly appreciated.

Cheers

Vanessa