if you are in the uk tryi have to agree with everyone else, and go with build. buying a pre-built you're paying for labor and software that is of no use to you.
However, if you do want to look at pre-builts, check out Acer. they are real good quality and are the only company i know of that 99% of its tech support is based in America (texas to be exact).
for parts, if your in America go with newegg.com. They do not delive outside the US so if you don't live in the US it's kinda pointless to look there. I'm not sure if Tiger Direct ships outside the US....
I don't consider that to be a con. Most companies don't have good customer support, and they charge you to fix stuff anyways. I'd say build, better parts, cheaper price and more options for customizing. The only time I say buy a pre built comptuer is if you don't want to build, or are in a bit of a rush for a new PC.only con is that no costomer support
I disagree, the best customer support is coming to this board with your problems, I really don't think the posters here (including you celegorm) really know how helpful they are...the best customer support is looking in the mirror and asking yourself the question.