The exact location and time of origin of the Borg is unknown. However, it is believed that the Borg originated in the Delta Quadrant of our own galaxy, and are believed to have existed for many thousands of years.
The Borg And V'Ger
It has been speculated that the Borg and V’Ger, the entity encountered by the Enterprise in 2271, may have similar origins. The Borg began as entirely organic beings that have the synthetic added later, while V’Ger was a machine that “joined” with “the creator” to reach the next level of it’s existence. The final view the Enterprise crew have of V’Ger is that of the machine somehow joined with two people. It may be reasonable to assume from this that a cybernetic lifeform, such as the Borg, has been created.
However, on closer inspection, it would appear that the theory of the Borg originating from V’Ger is unlikely to be correct. This is due to a number of factors.
When the Borg Queen took a vessel back in time to 2063, in an attempt to assimilate Earth in the past, the Borg attempted to build a transmitter on the hull of the Enterprise to contact the Borg living in the Delta Quadrant at that time. However, the Voyager space probes 3 to 6 had not been launched as of 2003. Even if they had been launched by 2063, Voyager 6, from which V’Ger originated, would not have travelled to such a distance from Earth that would require the type of transmitter the Borg were building. Also, at this date, not only did V’Ger not exist, but it had not “joined with the creator” as it did when encountered the Enterprise crew, and so was not yet part human.
There have also been reports from species that the Federation has encountered that the Borg have existed for many hundreds or thousands of years. Guinan was one of the El Aurian refugees that was transported to Earth after the Borg destroyed her home planet in 2293. She understood that the Borg had existed for thousands of years. The Vaadwaur race, which Voyager encountered in the Delta Quadrant, reported contact with the Borg up to 900 years before. This would show that the Borg have been in existence since the 15th century.
The theory could be changed to give the theory that V’Ger originated from the Borg, rather than the other way round. In a visual presentation, V’Ger shows that it was once a much smaller craft, the NASA space probe Voyager 6. It fell through a black hole or wormhole, and encountered a machine planet, where it was repaired. Although details of this planet are unknown, it may have belonged to the Borg.
An Unofficial Theory
An unofficial explanation for the origins of the Borg was explained in Strange New Worlds VI. The theory states that the Borg originated on a planet that was being devastated by plague. The granddaughter of the planet’s ruler forced scientist to use a new treatment on her. Nanotechnology was introduced to her system, destroying the virus. The nanotechnology, however, was programmed not only to return her to how she was before the virus, but also to make her perfect. They changed her physiology and her brain, adding technology to them, and thus creating the first Borg Queen.
Her grandfather executed the scientists responsible, and attempted to kill her with gas. The attempt failed as she adapted to the extent that she no longer needed to breathe. She also became able to introduce the nanotechnology into the wall of the room, which melted it, thus allowing her to escape. She accidentally transferred some of the nanotechnology into one of her guards. This created a link between them and changed him in the same way it changed her. They assimilated their homeworld and then moved on to other worlds.
However, the Vaadwaur reported that nine hundred years before their encounter with Voyager, the Borg were not as advanced as they later became and were only a minor nuisance.