Brand new legacy PCs are for sale.

[Salmon Trout]

How can they be new when the CPUs they use went out of production almost a decade ago?  DDR RAM also hasn't been produced for a long time and nor have the chipsets on those boards.  They're refurbished at best, they can call it what they like but there is no possible way the PCs are new unless they hoarded a store of those parts when they wee brand new only to sell them at a loss much later on, which makes absolutely no sense.

It is just amazing what is lying around. The phrase is "New Old Stock" (NOS). Ebay has plenty of NOS Pentium 4s and DDR2 RAM; CPUs run from $4.99 up;  DDR2 modules and kits for not much (e.g. 2GB DDR2 PC4200 533MHz PC2-4200 DESKTOP 2X 1GB DUAL KIT $14.91). Motherboards likewise. There are companies who specialise in hard to find and rare stuff. As well as people who want them to build systems there are people who collect "new old" CPUs for their rarity value, as if they were stamps or paintings.

One of my hobbies is audio and hi-fi; I am gratified as a European to see that these days American builders of vacuum tube amplifiers are as familiar as I am with the European tube type naming system, and many prefer NOS British and Dutch made EL34 tubes over equivalent RETMA (US) tubes with the 6CA7 designation.

[Calum]

I stand corrected in that case.  I've seen some items advertised as NOS, but didn't realise there were enough, say NOS Pentium 4s out there to build a business on.

[Salmon Trout]

I stand corrected in that case.  I've seen some items advertised as NOS, but didn't realise there were enough, say NOS Pentium 4s out there to build a business on.

I don't think there are millions of them out there, but there is evidently a considerable amount of unsold inventory. Also I wouldn't totally rule out used items. As far as I know CPUs don't wear out, although the amount of time the silicon has spent over a certain temperature can shorten its life. I saw a 52 pound weight box of Pentium 4 CPUs on sale for $500.

[Calum]

I wouldn't rule out used items either, probably 90% of the PC gear I buy is used.
I was just surprised that there were enough NOS components to sell those PCs as new, it would be a lot more believable if theyw ere refurbished due to the amount of RAM, motherboards, HDDs, DVD drives etc needed.
As for CPUs wearing out, I've never seen one wear olut in normal usage to be honest - I've only ever seen them degrade and fail from out of spec voltage or temperature, or die as a result of the PSU or board giving up in some way.

[Geek-9pm]

This is not a endorsement. Here is a link to pictures of 486 motherboards for sale. There must be a bunch out there. Just look around.
http://www.aliexpress.com/wholesale/wholesale-486-motherboard.html
I think the big issue is the presence of a older PCI bus  and the serial ports and at least one parallel printer port. Before the widespread use of USB and plug and play, those ports where the interface to printers, plotters, label makers and even bar code readers. And other things. Like a burglar alarms.

Contrary to what you might think, , the USB standard does not fully replace these old hardware things. Personally, I have spent hours doing research on USB adopters  and cam to a stone wall.

[Geek-9pm]

One more time.   
This thread is so old almost forgot but I placed it here years ago. But just for the record, I continue to buy and use refurbished PCs. The best source I have found is eBay. Yes, you can get ripped off on eBay. But that is true elsewhere. You have to be knowledgeable and pay attention all the details in an advertisement you see on eBay or anyplace else. Building a brand-new PC to legacy standards is not easy. Some parts are no longer available. Still, legacy PC is the way to go for some intense software applications that require the support of an older operating system. The older operating systems that are person might choose could be: Windows 98 SE, Windows 2000 and Windows XP professional. Some other versions of XP may be suitable for your application, so don't refuse Windows XP home edition just because it lacks some of the features found in the professional edition. However, many would discourage the use of Windows XP media Center version.
Now about legacy PCs. Some users want and need portable computers that are reliable and can be used with older software. I think my favorite would be the Compaq ct Armada series. They had very good audio, reasonable battery life and a very nice display. And of course, a nice keyboard. These old laptops could be used with a serial port which make them rather unusual. Also it had a docking port that could be used for external connections. It had a standard serial port which is useful with some older point of sale software systems where a serial port is needed to control a cash register.
Of course, one can run Windows XP as a virtual machine inside of Windows 8. But that requires the use of a fast computer that will work well as a virtual machine. But in some cases programs that have direct access to the hardware have some difficulty in a virtual machine. So in that case it's back to using legacy hardware with legacy software system.
The cost of building a legacy system from brand-new components is very, very expensive. The components are either not available or very overpriced.
In my opinion anybody who wants to make a business using legacy hardware should be prepared to make a significant investment in computers that are found at to yard sales or in pawnshops or wherever people try to get rid of stuff they no longer need. But there is a big problem. The less you have the expertise, getting an old computer to work again maybe Mort time-consuming than what you may have thought. That is why I would recommend buying a certified refurbished computer from someone who sells on eBay rather than trying to do-it-yourself. I've done it both ways on a small scale. I have taken older computers people had and got it working again and I have bots computers off of eBay that were not working condition. At the end of the day, my point of view is that it is better to let somebody else do the recertification and installation of the legacy software and offer you a warranty or guarantee. There are some companies that specialize in legacy hardware and will offer you a one-year warranty. Now think about that. In some cases even new equipment is not guaranteed for one year. Check it out.
I'm not trying to pump this post, but I don't like it when someone makes a broad statement about eBay without offering a credible alternative. EBay offers a large body of vendors you can choose from. Trying to locate a reliable vendor on your own is a lot of work. So my advice is choose your vendors off of eBay rather than otherwise. On eBay they have to meet up to a set of standards that are set out by eBay and are these people lose their reputation the lose their place on eBay. With vendors that have their own website, it is hard to know what the true history is of their company. They could post anything they want on their own website.
This is the end of my rant. I still think that you want legacy hardware you should shop eBay first.