wats the 2nd series of .hack// ?

Question

In ORDER
NO MAnga series!

Answer 1

If you are referring to the official TV series.

1) .Hack//Sign
(29-episodes)
The first .hack series based in the year 2005. A computer virus called "Pluto Kiss" destroys the networks of computers all around the world, subjecting the cyberspace to severe restrictions. Two years later (About ~2007), as free access to the networks recovers, people are now crazed over a full-immersion virtual gaming environment called "The World." However, when reality and virtual reality collide, a whole new adventure unfolds as a mysterious accident leaves Wave Master Tsukasa permanently logged in.
http://en.wikipedia.org/wiki/Hack_sign

2) .Hack//Legend of the Twilight
(12-episodes)
also known as .Hack//Legend of the Twilight Bracelet or .hack//UdeDen
Originally a manga series which was adapted into a 12-episode anime of the same name. It's about a pair of twins that are separated--Rena and Shugo who met up in The World. Set four years after the .hack games. (About ~2011)
http://en.wikipedia.org/wiki/.hack//Legend_of_the_Twilight

3) .Hack//Roots
(26-episodes)
.Hack//Roots is the prequel to the .Hack//G.U. videogames. It follows the story of Haseo, a Multi-Weapon and member of the Twilight Brigade guild. Set eight months before .hack//G.U. (About 2015~2016)
http://en.wikipedia.org/wiki/.hack//Roots

Some more background information:

.Hack//Liminality
(4 Special Episodes that comes with PS2 games)

Total of 4 volumes, it shows the 3 characters and how they investigate as to why several people have fallen into a coma while playing the game. (The time frame should be around ~2007, same period as in .Hack//Sign)

Vol. 1: In The Case of Mai Minase (with .hack//Infection)
Vol. 2: In The Case of Yuki Aihara (with .hack//Mutation)
Vol. 3: In The Case of Kyoko Tohno (with .hack//Outbreak)
Vol. 4: Trismegistus (with .hack//Quarantine)
http://en.wikipedia.org/wiki/.hack//Liminality

.Hack//G.U (PS2 Game)
The series encompasses three gamesfor the PlayStation 2 console.
Vol. 1 Rebirth
Vol. 2 A Voice that Reminds Me of You
Vol. 3 At a Walking Pace

The sequel series starts off in the year 2017, seven years after the events of .hack. In the seven years that have passed, not only has ALTIMIT OS been replaced by ALTIMIT MINE OS, but The World has become The World R:2.
http://en.wikipedia.org/wiki/.hack//G.U.


The three anime series is basically unrelated (except for the "virus and the world"), and based on different characters. It's totally alright to watch any of those without referring to other anime/game, unless you are a super .Hack fan.

Answer 2

it goes like this:
.hack//AI Buster (manga)
.hack//sign
.hack//liminality (dvds comes with the games)
.hack//legend of the twilight bracelet
.hack//Roots

Answer 3

Are you talking about .hack//legend , maybe?