The BBC has confirmed that 120,000 PC users have downloaded its new catch-up TV software, iPlayer.

The company expects half a million users will download the presently Windows-only application within the first six months of availability. A similar number of users already exist for Channel 4's 4OD service.

Jeff Richards, vice president of digital content services at Verisign, the technology firm behind both services, told MediaGuardian that the iPlayer: "Has had more creative thinking and more thought put into it than any other similar product and is one of the most advanced platforms of its kind."

However, the BBC continues to face criticism for its decision to make its service Windows-only, and is understood to be working to address this.

"We are committed to making it as easy as possible to use BBC iPlayer. Developing a version for Apple Macs and Microsoft Vista is absolutely on our critical path," said BBC director of future media and technology, Ashley Highfield.

iPlayer is a free catch-up service for UK licence-fee payers. Users can download shows which they can store for up to 30-days. These shows integrate digital rights management (DRM) technologies which make it impossible to view archived content for more than seven days following the first view of the show.