Can consider getting an Intel i3 NUC and just mount it to the back of a monitor/TV with vesa mounting. Great for a HTPC or general usage PC.
All you need is the NUC itself, laptop RAM, an mSATA SSD, and a wifi card (if you choose to use wireless instead of ethernet). Plug in a mini HDMI to HDMI cable to your monitor and you're good to go.