Ghosts I–IV (also known as Halo 26) is the seventh studio album by Nine Inch Nails and was released on March 2, 2008. It contains 36 instrumental tracks and was recorded in ten weeks of autumn 2007 and is the first Nine Inch Nails album released without a record label contract. Initially expected to be a five-track EP, the album is presented in the form of four nine-track EP's. The tracks do not have names, and are only identified by their track listing, position, and album art.

The album's initial release on the official Nine Inch Nails website suffered problems as the website was inundated with traffic, and was not fully operational until March 4, 2008 because, according to Nine Inch Nails frontman Trent Reznor, they needed to add extra servers to the site to handle the influx of downloaders. The album is also available for download on Amazon MP3. A 40-page PDF document of the album's liner notes was included with the official downloads. The PDF can also be requested for download at the official website. A week after the album release, the official Nine Inch Nails site reported over 750,000 purchase and download transactions, amassing over 1.6 million dollars in sales.

Ghosts I–IV was released online on March 2, 2008 on the official Nine Inch Nails website, without any prior advertisement or notice. Physical versions of the album will be released via RED Distribution on April 8, in both double CD and 4-LP formats.

The album is licensed under a Creative Commons Attribution Non-Commercial Share Alike license. Reznor states that an "exciting partnership and experience regarding this release" will be announced soon. Reznor has also stated that "more volumes of Ghosts are likely to appear in the future".

Several tracks from Ghosts I–IV were used as incidental music in episode 352 of the National Public Radio program This American Life, entitled "The Ghost of Bobby Dunbar".

* Trent Reznor – performance, production, art direction
* Atticus Ross – programming, arranging, production
* Alan Moulder – engineering, mix engineering, production
* Alessandro Cortini – guitars (4, 11, 17, 20, 24, 28), bass (4), dulcimer (22), additional electronics (19, 22, 29, 33)
* Adrian Belew – guitars (3, 4, 7, 10–11, 14, 16, 21, 25, 27, 31–32, 35), electronics (25), marimba (30)
* Brian Viglione – drums (19, 22)
* Tom Baker – mastering
* Rob Sheridan – art direction, photography, visual and physical elements
* Artist in Residence – art direction, photography, visual and physical elements
* Phillip Graybill – photography
* Tamar Levine – additional photography

Source: Wikipedia