I pinched this list from various places, mostly from people on this site. I was originally going to make one based on stuff that I know, like Intel duel core and nVidia card and whatnot, but I saw people recommending these components because they are so energy efficient and stuff, so I've priced one up using them and I just want to check it will all work together and will be a good HTPC. I'll be using it with Vista 64bit Ultimate.
Here goes:
Motherboard
Abit A-S78H, AMD 780G, S AM2+, PCI-E 2.0 (x16), DDR2 1066/667/800, SATA II, SATA RAID, Micro ATX
http://www.scan.co.uk/product.aspx?ProductId=25610
£46.45 Inc VAT
CPU:
AMD Athlon 64 X2 4850e AM2 Dual Core 2.5GHz, 512KB x 2 Cache, Retail
http://www.scan.co.uk/Product.aspx?WebProductId=807038
£44.38 Inc VAT
Heatsink and Fan:
Scythe Mini Ninja Heatpipe CPU Cooler S478/LAG775, AMD S754/939/940/AM2
http://www.scan.co.uk/Product.aspx?WebProductId=657369
£27.60 Inc VAT
CD/DVD/HD-DVD/Blue Ray
LG GGC-H20L Lightscribe SATA 16xDVD±R +RWx8/-RW x6 Also READS - Blu-Ray & HD Disc's black - Retail
http://www.scan.co.uk/Product.aspx?WebProductId=729076
£66.73 Inc VAT
RAM:
4GB (two packs of 2x1GB) Corsair TwinX XMS2, DDR2 PC2-6400 (800), 240 Pins, Non-ECC Unbuffered, CAS 4-4-4-12, DHX
http://www.scan.co.uk/Product.aspx?WebProductId=585723
For 4 gig:
£86.10 Inc VAT.
Hard Drive:
320 GB Samsung HD322HJ Spinpoint F1, SATA 300, 7200 rpm, 16MB Cache, 8.9 ms
http://www.scan.co.uk/Product.aspx?WebProductId=867043
£35.24 Inc VAT
Storage Hard Drive (quiet/low power consump.)
1TB (1000 GB) Western Digital WD10EVCS AV-GP, SATA 300, 7200 rpm, 16MB Cache
http://www.scan.co.uk/Product.aspx?WebProductId=864868
£110.41 Inc VAT
Case:
Antec Fusion 430HE Multimedia Case
(My friend has an unused one of these which he is going to sell me for a decent price)
Graphics Card:
256MB Sapphire HD3470 PCI-E 2.0 1400MHz GDDR3, 800MHz GPU 40 Cores, HDTV/2xDVI-I HDCP Ready Passive
http://www.scan.co.uk/Product.aspx?WebProductId=770339
£34.30 Inc VAT
Keyboard:
Logitech Dinovo Edge (New) Cordless Keyboard, BackLit Keys, Bluetooth USB 1.1/2.0, Black
http://www.scan.co.uk/Product.aspx?WebProductId=579460
£110.67 Inc VAT
Wireless/Wi-Fi Card, with Antenna:
Abit AirPace PCI-Express 54Mbps Wi-Fi Card with Antenna and Software AP - A World First
http://www.scan.co.uk/Product.aspx?WebProductId=530773
£9.27 Inc VAT
I picked that little PCI-Express Wi-Fi card because I wanted to leave the PCI slots free in case I decide to get a TV card and Sound Card. I'm going to listen to the on board sound chip first before I decide. I read good things about that little Wi-Fi card anyway, so if all goes to plan, I'll never use the PCI slots.