Simonyi, Fyodor Yurchikhin and Oleg Kotov joined another cosmonaut, Mikhail Tyurin, and Nasa astronauts Michael Lopez-Alegria and Sunita Williams, to hear greetings from friends and relatives at mission control over a crackly satellite link-up.
Simonyi became a billionaire after helping develop Microsoft's Word and Excel software.
He said it was "really an honour to be here on this outpost".
He had already filled three or four pages of a notebook "recording every moment of this flight", and said he would post his impressions on his blog.
Simonyi, 58, was born in Hungary and emigrated to the US where he joined Microsoft when it was a start-up.
He helped develop some of the company's flagship programmes and now runs his own firm.
Martha Stewart, the American lifestyle guru to whom Simonyi has been romantically linked, packed him an aluminium hamper containing quail roasted in wine, duck breast with capers and rice pudding.
Russian space officials said Simonyi planned to share the meal with his colleagues on Thursday.
He is expected to head back to earth on April 20.