Well... we have a number of them around the house... So I've gotta jump in on this!
My laptop: Acer Extensa 5620 - 2.0ghz Core2Duo - 4 Gigs DDR2, 250gb
Her Laptop: First gen Macbook - 2.0 CoreDuo - 2 Gigs DDR2, 250gb
Living Room HTPC: CoolerMaster 360 Elite Case, AMD 7750 BE (2.7Ghz x2), 4 gigs DDR2, 2x 500gb, 1TB, BR Drive, AMD HD6750
Bedroom HTPC: Dell Dimension E510, 2.6ghz Pentium D, 3 gigs DDR2, 160gb, NVIDIA 8300GS
Guest Room HTPC: Acer Aspire 5570 1.73ghz CoreDuo, 2 gigs DDR2, 80gb
Randomness: Dual 867ghz G4 Powermac, 1.5 gigs DDR, 80gb
The HTPCs are all running Win7, my laptop is running XP (the DHP works!), the Macbook is running 10.6, and the Powermac is running 10.5!
Nothing cutting edge, but they all do what they're supposed to do!