Sorry for the double-post but I neglected to mention something and I didn't want you to miss out on it: The two main reasons why you'd want to ask a friend/acquaintance to assemble a machine for you would be because it will be significantly cheaper and you will get to enjoy it for longer.
An occasion, this can lead to silly situations. My current PC is over a decade(?) old and refuses to break down. If [Certain MMORPG] ever releases in the west, I "might" need to buy a new PC, because my current one wouldn't meet that game's minimum hardware requirements.
(Of course you never know for sure until you try - they might just have been cautious when the publisher revealed their requirements.)
Yatsufusa
Some advice for when the time comes: Don't buy a computer 'off the shelf'.
You probably have an expert among your acquaintances who will be able to pick the components you actually need, assemble them for you, and will have fun doing so. (And then you can blow all that extra money on an overpriced Tower Chassis. ;) )
G2961
I would never buy a branded or just a ready-made computer, since the margin on them is very large, and there will be no sense from the hardware inside