Anne Muir, 58, had 7493 digital music files and 24,243 karaoke files -- worth an estimated £54,792 in the mainstream market -- on a computer at her home in Ayr.
The nurse was caught after a joint investigation was launched by the British Recorded Music Industry (BPI) and the International Federation for the Phonographic Industry (IFPI).
It is understood they tracked Muir down after she uploaded music on to the internet, making all of her details public.
The two bodies made a formal complaint to Strathclyde Police and officers obtained a warrant to search her bungalow in the town’s Gordon Street. They raided the property on June 27, 2008 and seized her computer equipment.
It revealed she was part of a “sharing hub”, which meant users within her network could download music from her, Ayr Sheriff Court heard yesterday.
Muir, a mother-of-three and grandmother-of-eight, pled guilty to a charge of distributing articles without the licence of the copyright owner “to such an extent as to affect prejudicially the owner of the copyright”.
Speaking from her home last night, Muir said: “I felt gutted it had happened. It was just an addiction, that was all. I don’t want to comment, I will have to talk to my solicitor.”
Depute fiscal Erin Campbell said Muir had downloaded files worth £54,792 on her home computer and had also made them available to others via a “peer to peer” file sharing application, in breach of the Copyright, Designs and Patents Act 1988. It is understood she uploaded the music on to the Direct Connect hub.
Each music file can be sold for 84p and the karaoke files are worth around £2, Ms Campbell said.
Mirian Watson, district procurator fiscal for Ayr, said the conviction was significant to the music industry, which is estimated to lose about £236 million in revenue this year because of illegal downloads.
She said: “Illegally flouting copyright laws is tantamount to theft and not only deprives legitimate companies and artists of earnings, but also undermines the music industry as a whole.
“We will continue to work effectively with law enforcement in this area and to apply our robust prosecution policy.”
Defence lawyer Lorenzo Alonzi said his client, an auxiliary nurse at Ayr hospital, had not used the network for financial gain, but to build up her self-esteem after suffering from depression for a number of years. Her condition also caused her to hoard things, he claimed.
He added: “It has to be stressed that this offence was not committed from any desire to make money.
“Mrs Muir was not in any way trying to distribute on a large scale, she had a very big quantity of these files because she was hoarding -- a symptom of the severe obsessive personality disorder that she suffers from,” the defence lawyer said.
“She has, for many years, suffered from bouts of depression, which causes her to have extremely low self-esteem.
“Learning this new technology and picking up new skills gave her self-esteem a boost.
“But to be allowed into the network she had to have a certain number of files already.
“She suffers from an obsessive behaviour disorder, which has been heightened recently because of problems within her family and the stress of this case.
“The obsessive behaviour is the explanation for Mrs Muir having so many of these files, it causes her to hoard things.
“She has expressed genuine remorse for this and is severely embarrassed about it.”
Sheriff Jack McGowan deferred sentence until May 31 to obtain a psychological report.
David Wood, BPI’s director of anti-piracy, said: “The defendant illegally distributed music on a massive scale, causing significant harm to legitimate music companies.
“We will not comment further since the case awaits sentence.
“We would like to thank the Strathclyde Police and the Procurator Fiscal Service in Ayr for their diligent work on this investigation.”