Old.
Well, relatively speaking. Win7 64bit SP1 Intel Xeon CPU W3565 6GB Ram Nvidia Quadro FX580. I might mention also that this system does not render some of the link buttons properly and uses some proxy fonts for some of the text on this and other SU pages. For example up at the top of the page, there is the group of buttons for Settings, Messages, Posts etc. The buttons are little boxes with little letters in them. So it is with the Login button at above right. They work, but they don't look right. Actually that is an old problem that I contacted Gabor about in the past.
Edit: I use Firefox currently at v42