A teenage girl found indecent images of children on a second-hand laptop she had been given for her birthday.
Following the discovery, police launched an investigation which led them to the laptop's former owner, James Dell.
Officers searched Dell's Burbage home and found hundreds more indecent images of children, plus other extreme pornography, on his computer equipment.
Prosecutor Neil Bannister told Leicester Crown Court 60-year-old Dell traded in his laptop at a shop in Hinckley on January 16, 2010.
A week later, the computer was bought by a man for his daughter's 16th birthday.
"To her distress, she uncovered some files which indicated there may be some disturbing images," said Mr Bannister.
He said the girl's 11-year-old sister had also used the computer, although she had not seen the images.
"The elder daughter informed her father and he was angry and distressed," said Mr Bannister.
The father called the police, who retrieved the laptop, and subsequently searched Dell's home, in Flamville Road.
Computers and memory sticks were seized and analysed, uncovering 717 indecent images – 283 at level one, the lowest category of seriousness, 55 at level two, 144 at level three, 224 at level four and 11 at level five, the most serious category.
Five examples of extreme pornography were also uncovered.
Dell pleaded guilty to 10 counts of making indecent images and two of possessing extreme pornography.
He was jailed for eight months, banned from working with children and placed on a sex offender register for 10 years.
Judge Simon Hammond said: "Any right-minded person would be utterly disgusted by some of the images I have had to see.
"How anyone could find them attractive I know not. The gravity of this offending is that young children somewhere in the world have been grossly sexually abused to create these images.
"Their lives have been ruined. These children in these images will never be the same again. Their innocence have been stolen."
In mitigation, James Varley said many of the images were duplicates and that not all were accessible to people without specialist computer knowledge or software.
Mr Varley said Dell had discovered child pornography on a computer he bought at a car boot and had then sought out more.
"He accepts that he did find them gratifying," said Mr Varley.
"He has family members in court who have to hear that and he finds that crippling."
