Home versions of Windows XP or Vista can be licensed one of two ways. The first is an OEM (Original Equipment Manufacturer) license, used when Windows is preinstalled by major manufacturers like Dell, Gateway, or HP or by smaller companies that assemble generic systems using off-the-shelf parts. (Microsoft refers to these as System Builders.) Copies of Windows with OEM licenses are tied to the computer they came with and can’t be transferred to another system.

The second is a retail license, which is what you get when you buy a boxed stand-alone copy of Windows from a store. Unlike OEM licenses, retail licenses are transferrable between computers, as long as you uninstall the OS from the original system before installing it on another one.

To see what kind of license your system’s copy of Windows has, check the Windows Product ID, a 20-digit number you can find within the System Properties dialog box—right-click My Computer in WinXP (in Vista it’s called Computer) and choose Properties. Your copy of Windows is an OEM version if your Product ID contains the letters “OEM”; otherwise, it’s most likely a retail version.

Ordering Replacement Discs

If your system is running an OEM version of Windows, you should contact the system manufacturer to obtain replacement Windows discs. You’ll usually find the vendor’s support contact information in the aforementioned System Properties dialog box, or do an online search for the information.

Policies vary by manufacturer, so the information you’ll be asked to provide and the cost, if any, of the replacement discs will depend on the company you’re dealing with. To get a sense of what you might expect, we got in touch with Dell to request a replacement copy of Windows XP Home Edition for an Inspiron notebook that we had bought back in 2004. Because we were on file with Dell as having purchased the system, we were told there would be no charge to send us the replacement and to expect shipment in three to five business days. (As it turns out, we actually received a set of discs the very next day.)

We also contacted HP about ordering a WinXP Media Center Edition disc for a three-year-old Pavilion desktop system that we did not originally buy. (It was given to us used.) The support representative directed us to a Web page for the specific system model where, upon entering the system’s serial number, we were able to order a set of replacement discs for just under $16, including shipping.

If your system was built by a System Builder that's unwilling or unable to offer disc replacement (maybe they no longer exist), you may be able to order a replacement disc directly from Microsoft.

To use this online ordering system, you’ll need to provide the COA (Certificate of Authenticity) number for the system’s original copy of Windows. (The COA is the small rectangular sticker that’s usually found on the side, back, or bottom of the PC.) When we used the system to order a WinXP Media Center 2005 replacement disc for a custom-built PC whose manufacturer had since gone out of business, the site quoted a price of $30, including shipping.

If you want to replace a lost disc for a retail copy of Windows that you bought, you have to talk to Microsoft; literally, because you can’t order a replacement online. Call the Microsoft Order Desk; it’s open Monday through Friday from 5 a.m. to 7 p.m. Pacific time. (The number is 800/360-7561 for U.S. residents or 800/933-4750 from Canada.)

Note that Microsoft will charge a small fee for replacement discs (how much depends on your circumstances), and you’ll likely be asked to fax in a dated copy of a sales receipt as proof of purchase.

Buying New

If you don’t have an OEM version of Windows or aren’t the original purchaser of a retail copy, you’ll need to buy yourself a new copy of Windows. When shopping for one, you should stick with reputable and well-known retailers to minimize the possibility of getting questionable software. If you prefer to do your Windows shopping online, be especially wary of buying from auction sites and definitely steer clear of unsolicited email (spam) offers. Also, be aware that no one other than Microsoft is authorized to sell Windows via a digital download.

Microsoft has a special Web site you can check out (tinyurl.com/63zebd), with lots of information about how to distinguish legitimate software from counterfeit. It even includes pictures of bogus copies of Windows so you know what to look for.

In order to be licensed properly, you’ll need the full version of the operating system rather than the upgrade version, and a bona-fide retail copy of WinXP Home will cost close to $199. That’s the list price, though you will often find it for a bit less at online retailers such as Amazon.com (www.amazon.com), Newegg (www.newegg.com), or TigerDirect (www.tigerdirect.com). Microsoft stopped selling boxed copies of WinXP to retailers as of June 30, 2008, but they’re free to continue selling WinXP as long as they have it in stock. As of this writing, we found it for sale at several well-known store chains and online retailers, but it will get harder to find as time goes on.

Therefore, if your system's specs are up to snuff (see the System Requirements chart), consider Vista Home Basic (an old PC probably doesn't have the horsepower for Vista Home Premium), which also costs $199. Before taking the plunge, download and run the Windows Vista Upgrade Advisor (tinyurl.com/63t642) which will check for driver compatibility.

Before you spring for a new copy of Windows, consider whether the cost is worthwhile given the age of your system. Spending nearly $200 on new Windows for an old PC may not make a lot of sense when for not much more than $300, you can buy a brand-new entry-level desktop, (or for around $500, a notebook).

When shopping for WinXP or Vista, (especially online, including at the sites mentioned earlier) you may come across OEM/System Builder versions of Windows for sale that are a lot less expensive than the full retail versions. You can buy them, but before you do, you should be aware of a couple of important limitations OEM/System Builder versions impose. First, they don’t come with support from Microsoft, and perhaps more importantly, because OEM licenses are forever tied to the system they’re installed on, if you want to move that copy of Windows to a new system in a year or two, you’ll be out of luck.

The Bottom Line

So if your system is running an OEM version of Windows or a retail version that you bought yourself (and you can prove it), you’ll most likely to be able to get a low- or no-cost replacement disc. Only when you’re aiming to replace a retail copy of Windows you didn’t buy will you need to bite the bullet and shell out for a new copy of your own, and in some cases, you may decide that getting a new system to go along with it justifies the extra cost.

by Joseph Moran