The HD Loader is an application (.ELF) for your PS2 that you can run off your memory Card, an USB Stick or a CD an then load your games off the Hard Drive that you can connect over the Network Adapter with you Fat PS2.
I may try the new ram site, and download more RAM to my Switch. Not sure if ddr3 is the right ram
for it tho. Edit- no it uses floppy Ram, just like @AncientBoi