Totally necroposting, but I couldn't get on to the forums for about a month for some reason.
I've got a hard drive in my PS2, but I use it in conjunction with a hacked bootloader that runs from a memory card and loads some small HD loader (also on the memory card, if I recall) to load games directly from the hard drive. Or maybe the loader is on the HDD and the memory card runs it directly? I haven't seen my PS2 in years, so I really don't remember anything except that the setup process was an absolute pain in the ass. My PS2 is getting really long in the tooth, and it stopped recognizing games that were on the blue-backed regular CDs (in my case, Gradius V, Way of the Samurai, and Skygunners), though games on DVD media still play just fine. All my loader discs for import titles were CD based, which meant they wouldn't work either, but running from the hard drive I can completely bypass region restrictions as well.
I can't give a whole lot of details off the top of my head. It works, as I said, through some sort of loader installed on the memory card; apparently on boot, the PS2 looks to the MC for things like drivers for the DVD player or diagnostic/service utilities, and someone found out a way to exploit that. I've got the official BB Unit, but a totally unofficial 20GB (I think) drive. I'm not sure if this setup works at all with games that can legitimately install data to an official drive present.
I don't know if any of that is what you were interested in, but there it is. I'm moving in about a month and a half and will probably pull out the PS2 again after all that is done, so I could check on what exactly the setup is, if you'd like.
You also distaste me with passion!