Off to build a PC

Well, I was planning until about 3 hours ago to come home and game and blog to begin my 5 day weekend, but I got an urgent call to come help a buddy from work put together a PC that is a Christmas gift for his mother in law, so I am in and out of the house quicker than you can say happy Hanukkah/Christmas/Kwanzaa/holidays. I know the system was a P2, and I know he found a good deal on a trade in upgrade, but I am not sure what all has to be done, and what all I will be doing. All I know is in exchange for the labour, I am getting dinner. It should be interesting to see if I can build a PC from scratch(or close to scratch) with a proper boot the first time. I have rarely had to completely assemble a PC, most of them have come at least partially together.