Kajoq - Unfortunately, yes you will have to purchase the PS2 network adapter. Tony Hawk (and I think one other game that came out around that time...) was the only game that supported that USB adapter (actually I think it worked in one or two other games). But Sony has already said that since then all games will only support the PS2 Network Adapter. I found this out the hard way as well, I had a USB network adapter and tried to get it to work with EQOA. After researching it on the 'net I found that THPS was the only game that was able to use the USB adapter...sooooooooo to sum up, save the pennies and go buy the official network adapter.
(phew! there I go again...getting all long winded!

)