My answer depends in part on exactly how you define "use regularly". If by "use regularly" you mean utilize for direct user interaction with the machine, then

My answer depends in part on exactly how you define "use regularly". If by "use regularly" you mean utilize for direct user interaction with the machine, then that would be a Compaq laptop from 2006 with 768M of RAM and an AMD Sempron CPU. If by "use regularly" mean "use to perform a task" then that would be a Supermicro dual Pentium-2 400Mhz system with 512M that acts as a PVR scheduler/recording driver. I've long since lost track of exactly when that motherboard was purchased, but it was somewhere in the 1998-2002 time frame. That puts it at somewhere between 11 and 15 years. If you'd asked this question last year I could have answered an old PentiumPro box (with something like 128Meg or 256Meg of RAM) that a buddy from work gave me that was acting as an internet firewall. It likely hailed from the 1995-1996 time frame. But I retired it last year in favor of an old Pentium4 Thinkstation that I got from a local store in their "refurb" section. I have no idea of what year the Thinkstation hails from.