On4 is the latest voice over IP (VOIP) service from relatively new company On Instant. If you've heard of Skype, you'll be familiar with the idea - using secure peer-to-peer Internet connections to talk to (or send voicemail or text messages to) other On4 users.

The free download is around 6MB and registration only requires basic personal details. After installing and logging on, you are presented with the main On4 screen, which is uncluttered and self-explanatory. From here you can search for contacts worldwide or send emails to friends to get them to join up. You can set your privacy level so only the contacts in your address book can call you, or you can let any On4 user get in touch.

Audio setup is implemented poorly at the moment - there's no built-in audio wizard or online help to tell you how to do it - but On Instant told us it is rectifying this. On4 works with any microphone/speaker setup or USB handset, but we had to fiddle about with Windows' audio settings to get our USB handset to co-exist with our PC's speakers. A human operator is always on hand to help.

Voice quality is superb, with little discernible lag and none of the cracks and pops usually associated with VOIP traffic. Video calls aren't offered, but you can add a photo to your caller ID.

On4 in its current incarnation is an interim release. Version 2 is imminent, with a totally revised client and extra services such as conference calling and eventually the ability to call landlines or mobile phones. But as it's free, try it and see what you think.

Contact: On Instant 01534 746 533
www.on4.com

System requirements:

• Windows 2000/XP Home/Pro
• 128MB
• 5MB hard disk space
• DirectX 8 or later
• Soundcard
• Headset, speakers/microphone or USB hand/headset

Price:
RRP: Free download.