CHALLENGE ACCEPTED!
Original Build (03/2007)
Apevia MX-Pleasure Full Tower
Intel Core2Duo E6300
2x1GB DDR2 800 MHZ
Gigabyte GA-965P-DS3 motherboard
Zalaman CNPS9500A Heatsink
Seagate 320GB HDD
Thermaltake 250 watt Graphics Card PSU+Stock 500 watt Apevia PSU
6600GT (Spare GPU)
Update 07/2007
Intel Core2Duo E6750
Gigabyte GA-P35-DS3R
Update 8/2008:
Corsair XMS 2x2GB DDR2 800
Xigmatek 750watt PSU
EVGA 9800GX2
The only thing that has changed is swapping out of HDDs and a new GPU when the 9800GX2's heatsink fan and EVGA supplied a new, different model to me (GTX 285) sometime around 2010.
Still usable for me as a gaming PC.
Other random facts:
DDR3 launched in 2007, but really picked up pace around late 2009 (which is why the above PC didn't use DDR3; the cost/benefit wasn't worth it). Today, we're now seeing the initial introduction of DDR4, but we most likely won't see it hit mainstream use until 2016. So in the past 6 years, we've seen really only one change in the RAM standard, if you want to start from when the RAM standard is at the mainstream level.
As for GPUs, in regards to nVidia there's been the introduction of 8 new tiers or families of GPU's if we start from the Geforce 9xxx Series (like my 9800GX2). And there are mulitple types of GPU's within each family, totaling more than 70 types. Considering there's been more than 120 models of new GPU's if you go back a further 6 years from 2008, any informed builder that knows their hardware development history will not be surprised by the rapid changes and updates that we find in GPU development. Really, the average family development is 1.5-2.5 years for significant changes (which relates to the family change) Nvidia went from Fermi to Kepler after about 2 years; Tesla to Fermi around 3 year.
Software wise. Let's see, Windows XP was released back in 2001 and has only now been phased out as support in 2013/2014. Vista was released in 2007, but everyone hated it. So in 2009, Windows 7 was released with widespread success. But then, Microsoft screwed up trying to follow Apple's lead with Windows 8 release in 2012.
Windows 7 is still currently in use, but support appears to be ending in 2015/2016.
Windows 8 and 8.1 will be leapfrogged when Windows 10 is being released, if the rumors of those with Windows 8 can get a free upgrade to Win10 is true.
Windows XP is still used, but mostly in the business community where upgrading outdated PCs can be a costly and time-consuming event. Most likely, I would expect all XP PCs to be gone a year after Windows 10's release. So if we go back the 6 years or so, we've seen really only 3 changes to the OS for Windows (XP -> 7 -> 8/8.1) If you want to count Vista, then you shouldn't be recommending parts to people as a lot of gaming PC builders avoided Vista.
Chipset changes follow CPU changes for the most part, and it's now getting late for me to keep typing this.
TL

R I have a 7 year old gaming PC that I can still play PC games on. Can it play the most recent games? Probably not, but then again, I don't expect it to. It plays the games I want it to play fine though: Minecraft, WoW (when I was still playing WoW that is), CoD4, Witcher 2, Dead Island, Half Life 2, Starcraft 2, AOE2, etc.
The main thing to remember is that the PC build's framework will last. He will only have to upgrade certain parts if he wants or needs to, most likely the GPU. Because if you don't adopt a 3 year upgrade timeline on the GPU, you will experience some lag or lower performance. As far as I'm aware, however, PC builders still aim for a 5 year life expectancy for their PC. Only those with lots of money or have professional reasons go with a higher turnover rate.
And we're deviating from the OP's reason for the thread. So I'm going to ask to lock the thread.