Quad core Intel Yorkfield 64 bit, 2.5 GHz x 4, with 4 Gb RAM.
It's only about 5 years old, but last time I upgraded, I kept the old operating system. I kind of resent the fact that each new version of Windows contains more misery than the last. (A lot of my working life revolves around repairing applications that have been broken by system software "upgrades", so I tend to avoid doing the same thing in my personal life. )
I've been meaning to convert to Linux, but never seem to find the time for the learning curve.