Why won't my PC recognise my monitor?

DRM, missing HDCP expected on HDMI.
Just speculating the HDMI port on the TV might be requiring a HDCP handshake. Is it a fairly new TV?

Yes, it’s a new TV and is HD Ready. According to your link it will have HDCP so this might be the issue but I’ve never heard of this problem.

It’s certainly only one possibility. Do you have any other HDMI screens into which you could try hook PC output ? I.e. are you sure the DVI-HDMI adapter is working ? And/or is the basic DVI output on the computer working into a DVI monitor ?
I’d try all of those if the right gadgets are lying around.

The adapter is brand new but I’ll try it with my main TV tomorrow to check it works. Good idea!

@dabbler‘s answers are very good ones.
And just because the adapter is new, doesn’t mean its not DOA. That happens fairly often with those little (often generic) odds and ends pieces.

I just wanted to make sure that you know that running a DVI through an HDMI adapter will NOT provide sound, you’ll need a seperate connection to audio. You may already know this, but this is a very common mistake.

@wds2 Good point about the sound. I run my projector that way, video only, and the sound goes into the ‘stereo’.

@flutherother
I just wanted to point out something….. you mentioned the TV is fairly new and HD ready.(an HD ready TV is able to display an HD picture but does not have a built-in HD tuner therefore it requires an external tuner) They stopped manufacturing HD ready TVs a long time ago. Presently TVs are either digital (with a built-in digital tuner) or HD (with built-in digital & HD turner)
Maybe the problem lies on the fact that you’re using an HD ready TV.

I tried connecting with my main TV but this doesn’t work either. It might be a cable problem but the source input is lit and identified on my monitor so the connection is recognised but no data is being processed.

The TV does have a tuner and plays digital TV broadcasts without any trouble.

I have a separate sound system for my PC so sound is OK.

Do you have a computer monitor with a DVI input that you could test the DVI output from the computer going straight to a DVI display?

I’ve got it sorted thanks. The DVI output from my PC was dead but fortunately there is a second connection which works great.