Barry Harkcom collected the images over 16 years and used technology designed to hide the images in his laptop.
But he told Bournemouth Crown Court he had become obsessed with cataloguing and that "porn leaves me cold - I find it incredibly boring."
The court heard Harkcom, a father and former IT specialist at Credit Plus in Fleetsbridge, was arrested after police raided his Wimborne flat in April last year.

He was in bed at the time and lunged at his laptop in a bid to switch it off before police could seize it.
The court heard that such was the extent of Harkcom's computer knowledge, police would have been unable to see what he had been viewing if he had managed to switch it off.
Harkcom, 56, later told officers they would have been "screwed" if he had managed to switch it off.

Defending his actions, he said: "I was in a very confused state. I had dreamt about that situation for years. I was not convinced it was real."
He said he had no recollection of watching child porn videos before going to sleep and said he only remembered watching Yes Prime Minister.
He told the court he had a strict, religious upbringing and bought porn videos in Soho at the age of 18 in a bid to rebel.
He added: "I have always had massive collections of pornography. Child porn was simply another category - I stumbled across it."

Harkcom, now of Library Road, Parkstone, admitted three charges relating to possession of around 73,000 images, nearly 1,300 of which fall into the most serious category of image. He also admitted a charge of possession of extreme porn.
Police seized a laptop and 48 hard drives from his home. They randomly analysed around five per cent of the material and believe there may have been a total of 20 million stills and moving images

Crying in the dock and mopping his brow with a handkerchief, he added: "I have a problem that having downloaded something, I can't delete it, I don't have the strength of character.

"It has caused me stress and anxiety for years. I have had nightmares about being raided by the police. I jumped for the power button because that's what I dreamt about doing for years."

He said anything he viewed was "for the purpose of organising it" and added: "It is bizarre, I know. I lost my job and got evicted all on the same day but the overwhelming relief far outweighs those incidents. I am a compulsive hoarder."

Prosecutor Stuart Ellacott told the court he believed Harkcom deliberately collected the images and tried to cover his tracks using coding, hiding the IP address on his computer and using software to permanently delete files called BleachBit.

Sentencing him to two years and one month in jail, Judge Brian Forster QC said Harkcom's defence "offends common sense."

He said Harkcom must be the subject of a sexual harm prevention order for 10 years and will be on the sex offenders' register for 10 years. His computer and hard drives will be forfeited.