Whilst not my everyday machine, I still use a HP/Compaq 6710b laptop running Windows XP. The only thing I've done is replaced the original 120GB hard disk with an SSD. I think my one has the 2 GHz Core 2 Duo processor.
Still a good machine that runs perfectly fine. Has older I/O which comes in handy sometimes (9-pin serial port, intergrated card reader that takes some of the older type memory cards, Type I/II PC Card slot...).
The battery is long gone, lasting about 2 minutes, just enough time to unplug and move somewhere else without powering down ;-)
Specs
here for any obsolete computer aficionados.
My daily machine is a desktop with 8GB RAM and a Xeon processor. About 4-5 years old now but still perfectly good for CPU intensive tasks. The video card isn't anything special, but I don't play games anyway.