Where can I buy parts to build a computer and where is a tutorial on how to build a computer?

As you have posted to yahoo answers UK I assume you are resident here, as other have suggested use partpicker but choose the UK site, it will direct you to English suppliers. There are many tutorials on how to build a PC, I would also suggest buying PC shopper in the newsagents for help HTH David

pcpartpicker.com is also an awesome spot to spec the whole thing out! It compares from sites like Amazon, NewEgg, and Tigerdirect (which will be the 3 cheapest places for consumers to find parts) My friend who knows nothing of building desktops asked me for help and sent me a link to her current build. I was amazed at how thorough and compatible of a setup she had picked with little knowledge of what to get! Not sure about a guide though.. I'm sure there's a bunch out there, but every motherboard is slightly different, so you would just have to familiarize yourself on what the ports do and what can be connected to them. Compatibility is a very big deal as well. If you just start buying parts at random, there's a chance the CPU won't fit in the MOBO socket, the ram might not fit your DIMM slots, etc. I recommend getting some supervision if you've never dismantled a desktop and put it back together before. It can get expensive if something breaks ;)

Newegg is the best spot, great shipping and the prices are excellent As for a tutorial, you can find several on YouTube