My apologies to those who have seen me post this on other forums, but I just love this HTPC because it's soooo quiet and cost me so little to build. Even though a year has passed since I completed it, I'm still very happy with it. The specs are very modest: Celeron M 1.4GHz on an Asus P4P800-VM mobo w/CT-479 adapter, 512MB RAM in dual channel, MSI Geforce 6200, Seagate 160GB SATA, Twinhan 1025 DVB-S, and Dvico FusionHDTV5 Lite. Its primary function is a Media Center DVR for HDTV and DVD playback on my projector, and it works wonderfully for that.
I can't take credit for the silence. This was an old Zapstation PC-based MP3 player that I gutted and rebuilt. I really did nothing to make it silent, Harmon Kardon did a really good job designing the case. It has rubber bushings suspending the HD (the HD does not make any metal-to-metal contact with its tray). The original cooling of the case is interesting, there is an inner wall with perforated holes in it and maybe 3/16" airspace between the inner walls and the outer cover which just has small holes along the bottom. It doesn't seem like that would be sufficient, but even after being on for several days, CPU peaks at 34C, GPU at 57C, and HD at 42C. The GPU and HD temps are kind of warm, but well within acceptable limits. It's so quiet, I can't even hear the hard drive. There is no HD LED so I have no idea when it's being accessed! It's so quiet the front panel LEDs are the only indicator it's on. Most of my efforts with this case was to make the VFD, front panel buttons, and original Zapstation remote work with MCE.
More pics here: