Am using Windows 7.

Was fiddling around with partitions and attempted to install a bootable Mac OS on one partition, but I think the software I used didn't see partitions, so I unintentionally clicked on the whole drive. Because it wasn't already formatted correctly, it failed and so I thought nothing of it.

Plugged it in the next day and no drive appeared in My Computer, its actually possible to find it again in Windows 7's 'Disk Management' and its saying that there is 2TB of unallocated space, leading me to believe that the partitions have been deleted.

I downloaded 'Stellar Phoenix Windows Data Recovery', but because it has no partitions, and cannot be seen in My Computer, its not appearing in the list of drives available for data recovery.

The data on the disk was not majorly important, but over the years I had gathered around 1TB of films, TV shows and home videos. I have the home videos on DVD thankfully, but it would be most inconvenient to lose the rest of it.

Thanks in advance for any suggestions

There are a few places where you talk about "it" but the subject isn't clear. You also mention "accidental format" yet you report having lost the original partition(s) - those are different things. So there's some confusion & ambiguity meaning I'm not clear exactly what you did.

If you are intent on a DIY recovery attempt, and are happy to take the risks of that (e.g. not enough experience to be sure that you won't make the situation worse), then clone the raw drive using suitable software that doesn't rely on cloning a filesystem. If you don't have Linux skills, then perhaps HDClone would be something to investigate.

That will mean you need another empty 2TB disk, or an equivalent amount of free space on another filesystem e.g. NAS box. By doing this, if any later recovery steps do make things worse, you can go back to your clone and restore it onto your working disk, and you're back to where you started ready to try something else.

I would be looking at your disk with a hex editor, to try to figure out what you did regarding formatting & partition deletion, but you need to know what you're looking for. Therefore for you, I suggest that after cloning the disk, you investigate TestDisk (Google it) to see if that can find your previous partition. Alternatively there are other commercial recovery software utilities which you could try-before-you-buy like GetDataBack, R-Studio and others. If they are as unsuccessful as your Stellar software, that suggests things may not be as simple as you described.

Good luck!