@ GUILT
Hey mate - I registered on this site just to post this message of thanks for your work and guide - I was pulling my hair out for about three days trying to get my 2Tb 'ex-Sky box' hdd fitted and working and now I have, after thankfully coming across your guide which appeared on a Google search page. I know you're aware of some issues so I'll try not to repeat them through gnashing teeth lol. I'll just let you know how I am doing so far based on your guide and information!
So far I got the 2Tb fitted, formatted - I followed your advice on partitions/folders and FreeHDDBoot. The drive is a Hitachi, and the drive is connected using a cheapo Gamestar SATA non-network hdd adapter, although it's also tested and working exactly the same using a Gamestar IDE adapter with Sata converter (although you can't get it inside the machine with that haha)
I've got a large collection of around 570 PAL original titles all ripped using three separate PCs (at the same time) using three instances of IMGBURN - It took about 30 hours to do this lulz.
As I was transferring the iso files to the hdd using HDL Dump GUI Helper, I needed to transfer games over as I was ripping them so it was a pretty intense project as I was glued to my computer for about 3 hours each evening over the course of three weeks, and each evening I ran routine tests of the drive and OPL etc to make sure things were showing up. ****When I had used about 1.3Gb of the hdd, Hddmanager would no longer run.**** I didn't realise this was something that would cause an issue later on so I carried on filling up the drive for a few days - with other ISO files I've 'collected' over the years, I'm now on to about 1.8Gb in use with a total of 660 titles, and probably room for another 100-150.
From switch-on, with OPL autobooting using FHDB, it takes about 40 seconds each time to get to the actual OPL HDD games list up on the screen - not a bad wait unless you're a persistent 'game hopper'. Game loading times are as fast as they are with a smaller drive but IGR obviously then takes 40 or more seconds to return you to the game list.
My main issue now, is the folder size set for the OPL folder - 2Gb? ...it's not going to be big enough to be able to use ART fully AND VMC, if I were to go to the extreme of creating an 8Mb VMC for each game. Although the chances of me ever getting to play more than half of these games are slim to none (there was some rubbish released, we're all guilty of owning, lets face it

) and as HDDManager is no longer functioning there is now only one way to increase the size of the OPL folder as far as I can tell - that is to delete up to a Terabyte of my ISO files just to see if it gets HDDManager to start working. I'm extremely unlikely to do this unless a program allowing batch-selecting of files to transfer appears. HDL Dump GUI Helper is the best program I've found for copying files to and from the 2Tb drive, but seriously, without a batch-select option, selecting individual files to move one way or the other is just PAINFUL.
Here's hoping an update for HDL Dump is released in the future with the extra features, now 2Tb internals are becoming more well-known on the PS2 scene.
So, I'm fairly happy and thanks to GUILT!
Oh, and for the people who say there is no point having a drive this big as there are not enough good games to fill it - I have done this because I can, and it's FUN!