First off, Im an apple man and build my own hackintoshes. My two sons have PC gaming rigs.
I have an Intel i3 550 plus a GA H55N USB3 motherboard (both 1156 sockets) left over from an old hackintosh build. I was thinking of building a HTPC with these components. The case I have has a 120w power supply and will not accept a graphics card. I dont want to buy anything else to go with this, so if it aint gonna work I'll just use them to build another hackintosh.
I dont want to play games on it, juts use it for simple stuff and watching movies and run xbmc.
You would most likely not be able to run this system on that PSU. The i3 550 requires 73W which leaves 47W (at max PSU load - not recommended for extended periods) for everything else in the system: RAM, fans (including case fans and CPU cooler fans if present), HDD, any drives (ex. DVD), USB devices (ex. keyboard and mouse). Minimal PSU for such a system would be in the 200+Watt area.