OS/2

Background
OS/2 is a series of operating systems initially developed by both IBM and Microsoft. The first version of the system was launched in December 1987 and newer versions were released until December 2001. After October 1994, the operating system would then be called "OS/2 Warp" due to the addition of several performance and GUI improvements, starting with version 3.0. It was targeted at professional and server computers. IBM discontinued support for the software on December 31, 2006. Two third-party vendors have developed the respective OS/2-based operating systems, such as eComStation by Serenity Systems, and ArcaOS by Arca Noae, LLC.

1st Screen (December 1987-December 1990)
Visuals: Same as the Windows 1.0/2.0 bootscreen at the time, but the Microsoft logo is replaced by the IBM logo, underneath the IBM logo is "Personal Computer", a border is around the text "IBM Operating System/2 Extended Edition 1.0", copyright notice (altered here) is underneath the bottom of the screen.

Trivia: This screen also appears whenever installing any version of OS/2 Warp, with the text on the frame border being different, and instructions about inserting the diskette seen below.

Technique: None.

Audio: None.

Availability: Appears on computers with OS/2 1.0-1.3.

2nd Screen (February 1992-August 1994)
Visuals: On a black background we see the copyright info of the operating system below. Above there's various boxes with various colored circles with the text "OS/2" inside them wiping from below piece-by-piece. Those boxes then disappear, followed by a bigger version of the logo forming the same way as the previous boxes. The copyright info changes to "Loading, please wait..." a second after the logo is formed.

Technique: Computer animation.

Audio: None for the original version.

Audio Variant: For the multimedia version, startup and shutdown sounds were added.
 * Startup: A "baseball charge" sound played by a trumpet.
 * Shutdown: People clapping.

Availability: Appears on computers with OS/2 2.0-2.1.1.

3rd Screen (October 1994-February 1996)
Visuals: On a black background we see a white box. On the top-left corner there's the IBM logo. The OS/2 box from before is seen near the right, rotated about 40 degrees to the left. The text "Times New Roman" is seen below. Below the box there's a copyright notice.

Technique: None.

Audio:
 * Startup: A low ascending synth note that builds up a sudden orchestra hit. This is actually a combination of two pieces of stock music from Network Music's ShockWave and Brainstorm music libraries, "Power Lift" and "Gothic Hit Chord".
 * Shutdown: A descending synth. (aka "Tonal Cascade" from the aforementioned ShockWave music library)

Availability: Only on OS/2 Warp 3 systems.

4th Screen (June 1995-2000s)
Visuals: On a black background, we see the warped text "Times New Roman WARP" on the center. Below the text is "Operating System/2 Version 3" and a copyright notice. The IBM logo is on the top right.

Technique: None.

Audio: Same as before.

Availability: Seen on OS/2 Warp Connect 3 systems.

5th Screen (September 1996-December 31, 2006)
Visuals: On a marble background, we see the warped text "Times New Roman WARP" on the center. Again, the IBM logo is on the top-right, but this time in white.

Technique: None.

Audio:
 * Startup: A calm synth theme with chimes. (aka "Mellow Rise" from Shockwave 4 - Stagers)
 * Shutdown: A loud whoosh, followed by the same descending synth from before, finished by some twinkles. (technically a remix of the previous track under the name "Wind Flowkeys Sparkle" from Shockwave 4 - Stagers)

Availability: It is found on OS/2 Warp 4 systems. Due to being the latest version of the OS and having a longer support, it's easier to find than the previous ones.