Hey there, I'm having the same problem here, I guess.
I recently bought this DIR-601 router, just to have a wifi connexion on my cell.
Anyway, I first tried setting up the router using the CD provided in the box, and I didn't even have to insert it to know it was not going to work, the CD being labelled as the installation CD for a wireless USB adapter, which for some reason found its way into that box, and it was of course no use for me.
So I then figured I would do the manual set up, using the 192.168.0.1 IP as said in the router's manual. Only trouble is, using the username Admin as requested (or even User) and leaving the password blank doesn't work at all, the page asks me a captcha, which for some reason, is nearly always wrong. And when it's not, it says 'Invalid user name or password, please try again.' Here's a capture of the log in screen

I then thought that I could probably find a driver somewhere on the web, but all I could find was a .bin file, wich I supposed to be a CD image, but that I could not mount on a virtual drive, even when converted to a .iso format.
So, I'm kinda clueless now, hope someone will have an idea, thanks by advance =)