Paris Olympics organisers said on Friday they were experiencing problems linked to the global IT outage, causing difficulties in handing out accreditations to athletes and officials arriving for the Games.
Airlines, banks, TV channels and other business across the world have scrambled following one of the biggest computer crashes in recent years, caused by an update to an antivirus programme.
"Like a lot of organisations, we suffered this global Microsoft outage," chief organiser Tony Estanguet told reporters, a week before the opening ceremony of the Olympics.
"All of our servers were affected this morning."
Estanguet added critical IT systems had not been hit but "for operations on the ground, to welcome new athletes, to welcome all the delegations, to issue accreditations, it slows down our operations."
Thousands of athletes have begun flying into Paris ahead of the opening ceremony, with the newly built Olympic village opening its doors on Thursday.
The organising committee said in a separate statement the impact of the outage was "limited" overall but it had also complicated the distribution of uniforms to the 45,000 volunteers for the July 26-August 11 event.
The IT problems have not affected Paris airport operator ADP, but "the arrival of some delegations has been impacted by delays to their flights," the organising committee added.
- Cyber risks -
Paris is putting the finishing touches to preparations for the global sporting extravaganza, the first Olympics in the French capital in a century.
The venues are on track, the weather has brightened up after months of rain, and the water quality in the Seine has improved, making outdoor swimming events in the river possible after months of suspense.
New data released on Friday showed the river was clean enough to swim in on six out of seven of the last days.
"We weren't necessarily expecting an IT outage a few days before the start of the Games," Estanguet said.
French authorities are on high alert for cyber attacks, however, either from criminal groups or nation-state actors, with Russian hackers viewed as a particular risk.
"It's absolutely certain and inevitable that ransomware attacks will occur during the Games," France's cyber security agency, Anssi, said on Thursday.
"Statistically, there is a high chance that ransomware attacks will affect actors who will be involved in the Games."
Elsewhere on Friday, the Japan Gymnastics Association (JGA) announced 19-year-old Shoko Miyata, a world bronze medallist and captain of Japan's women's gymnastics team, was being sent home for smoking and drinking.
Miyata was reportedly seen smoking in a private setting in Tokyo some time at the end of June or beginning of July and had allegedly drunk alcohol in a room at Japan's national training centre, JGA secretary general Kenji Nishimura told reporters.
- Love and diversity -
Estanguet was talking in Paris at an event with the creative team behind the wildly ambitious opening ceremony which is set to take place over a six-kilometre (four-mile) stretch of the Seine next Friday.
Around 6,000-7,000 athletes are set to sail down the river on 85 barges and boats, with around 3,000 dancers, singers and entertainers positioned on the banks, bridges and nearby monuments.
It will be the first time a Summer Olympics has opened outside the main athletics stadium, with up to 500,000 people set to watch in person from stands, on the river banks and the overlooking apartments.
Director Thomas Jolly, a well-known theatre director, 42, said the main theme would be "love" and the performances would celebrate diversity.
"We are a city of love, and also because in the world there is a lot of fractures," he explained.
"We want to say, we are all living together in the same city, the same country, the same continents and the same planet."
Jolly's plans have been criticised by some conservatives in France, but he said his work would be a celebration of cultural, linguistic, religious and sexual diversity.
"I think the people who want to live together in this diversity, this otherness, are much more numerous, but we make less noise," he told AFP.
"The evening (the ceremony) will be an opportunity to express it."
The ceremony has been hit by a strike threat, with around 300 entertainers threatening to stop work because of major pay differences in the troupe.
Another meeting between the CGT trade union representing them and the production company behind the ceremony, Paname 24, was planned for Friday.
By Adam Plowright