I'm worried people are just guessing who one of the passwords in this case belongs to. This is the problem with only being able to use new accounts (and tuna, who donated his account to science.)
You knew which ones to try it with, and thusly didn't have to do one of the trickier parts of the investigation.
here's the official walkthrough. Avoid if you haven't solved yet.
SPOILERZ
PART A
Clue 1: EVO's "HL1 map" thread. I reply in it, linking to the In the Beginning Tutorials. Click it.
Clue 2: Tuna has commented the In the Beginning tutorial linking to his recently uploaded map. Paste it.
Clue 3: Download the .zip, extract and open the .map in Hammer. It's empty. Check the .map in notepad? Oh my days, a password related to Monkey Island!
PART B
Clue 4: Evo also has a link in his Bio. It leads to a journal made by me many moons ago. The journal mentions an easy code to remember.
Clue 5: Supermatt mentions that BiscuitNinja likes Monkey Island. Connection to earlier found password is formed.
Clue 6: Logging in to BiscuitNinja's account, you find out that Billybop has the answer.
PART C
Clue 7: Supermatt, like so many before him also has a link in his bio. It leads to his very aesthetically pleasing website.
Clue 8: He mentions checking the source code. Doing so will reveal another password - Invader2003, and states that it belongs to the person with the answer.
Clue 9: Logging in to Billybops account reveals a private message from BiscuitNinja with the answer in code. Refer back to Huntey's journal.