Multi-monitor set up not working :'(

I have had a tri monitor set up for the last few years working perfectly. In my profile I have full PC spec that I've had it working on. The displays I've been using are: Samsung S24B300, Acer S240HL, and a Samsung 40" Smart TV (no longer connected).

I've just moved house, the PC was transported very carefully - not bashed at all. With moving house the TV that I previously had connected has now been disconnected and is set up in a different room. I'm going to be introducing a Sony 37" LCD TV to this system instead.

My graphics card - AMD Radeon 7800 series has the following connections available: Mini Display Port, HDMI, DVI.

I've currently got the Samsung S24B300 connected via DVI (DVI - DVI lead). I've got the Acer S240HL connected via HDMI (HDMI - HDMI lead).

I've got an active mini display port adaptor (DVI - Mini display port), ideally want to use this for the Acer monitor, I have a DVI - HDMI lead also.

When I have either one of the monitors connected it works perfectly. When both are connected it works to the extent you can see the Windows 7 logo during boot on both displays, but then when Windows 7 loads up fully it turns the Samsung off. In my old place it used to do this infrequently with the Acer display instead.

All of my cable's work perfectly as they work on their own with out the other monitor plugged in, Windows is fully updated, my display driver is fully updated (14.501.1003).

Can anyone help shead some light on this? I need to get this multi display set up working again.

Have you tried using WIN+P and selecting extend?

I haven't tried this, I will try tomorrow evening. But I doubt it'll work. The monitor appears to be in standby when the PC is on, but it isn't when the PC is booting, AMD Catalyst doesn't recorgnise multiple monitors, neither does Windows. I'm really confused with it all!