I have an early 2009 22" imac which has a mini display port. I have connected it to my hdtv in the past, using a hdmi-dvi cable and a mini displayport-dvi adapter, this works fine. However, I have recently bought a new, more powerful pc and want to use the imac as an external display. I have used the same connection, from my pc -hdmi-dvi-mini display-imac and set the imac in target display mode by holding t on boot, but it doesn't seem to get detected. Is this feature available on my model?

I have an early 2009 22" imac which has a mini display port. I have connected it to my hdtv in the past, using a hdmi-dvi cable and a mini displayport-dvi adapter, this works fine. However, I have recently bought a new, more powerful pc and want to use the imac as an external display. I have used the same connection, from my pc -hdmi-dvi-mini display-imac and set the imac in target display mode by holding t on boot, but it doesn't seem to get detected. Is this feature available on my model?

From the first link below....

Use an iMac with Thunderbolt as a display
If you have an iMac with Thunderbolt, any other Mac with Thunderbolt can use it as a display. The iMac will play both the video and audio from the other Mac.

Use a 27-inch iMac with a Mini DisplayPort as a display
If you have a 27-inch iMac with a Mini DisplayPort, any other Mac with a Mini DisplayPort or Thunderbolt port can use it as a display. Make sure you have a Mini DisplayPort to Mini DisplayPort cable.

Long story made short: You need either Thunderbolt or 27", so for you, target display mode is no-go.

For other options, see the other two links below.

Some Target Mode confusion here.

Holding down the T while booting will put you into Target Disk Mode.

Target Display Mode should be automatically recognised when the other computer is correctly connected to the bi-directional Mini DisplayPort. It can be manually activated by pressing Command and the F2 keys. It was available with the 2009 27" iMacs but probably not with the smaller ones.