We answer a lot of questions about Microsoft Windows OEM (original equipment manufacturer) software, including XP and Vista.  So here are the most common questions we receive with straightforward answers.  If you have questions that you'd like answered in more detail, please contact us.

Q: What's the difference between the OEM versions of Windows and the versions that are sold in stores?
A: OEM software licenses often cost less than half of the full retail equivalent, so with good reason many wonder if this type of license will fill their needs. First, it's important to note that OEM Windows is not crippled. Once installed, OEM Windows works exactly like the more expensive retail versions, including the same security updates, service packs, and program updates (like Media Player 11, Internet Explorer 7, etc.). This is the same Windows license that you'd receive with a new PC from Dell, HP, Compaq, etc.

So what's different? OEM versions of Windows are designed to be sold to system builders, so they have minimal packaging and only allow you to perform a full install; the option to upgrade from your older version of Windows is not available. Also, OEM Windows doesn't include free phone support from Microsoft because you, as the 'system builder', are supposed to provide it. However, some resellers on ebay offer installation support themselves. Finally, anyone can purchase OEM Windows. No laws or regulations prevent you from doing so.

Q: What are the differences between the different versions of Windows?
A: Let's start with Windows XP. Simply put, Windows XP Home is Windows XP Pro, minus some features designed for use in a corporate environment. For instance, XP Home cannot connect to a corporate domain or support multiple processors (XP Home does, however, support dual-core processors). Windows XP Home also has simplified networking options, but still has all the important networking, sharing, firewall, and routing functions that Pro has. So then basically, if you don't need to connect to a corporate network, then you probably only need XP Home.

With Windows Vista, there are several versions available that each support a wide variety of features. Most users will be happy with Vista Premium, and corporate users will need Vista Business edition. There is more information and a comparison chart on Microsoft's website.

Q: What will happen to any data that is already on my hard drive?
A: Installing Windows XP or Vista OEM will replace the operating system on the target drive (well, technically on a particular partition, but really most PCs only have one drive with one partition). So you will want to back up your data first, because most likely your data will be overwritten, lost.

Also, you could consider using an Upgrade version of Windows to migrate from an older operating system. But be warned: if your old operating system has problems, like spyware or viruses, then you may lose data if the upgrade fails.

Q: On how many PCs can I install Windows?
A: You are free to install Windows on as many PCs as you'd like. However, you won't be able to log on after 30 days unless you activate Windows with Microsoft. So the real question is...

Q: On how many PCs can I activate Windows?
A: One. This is true for pretty much all types of Windows licenses: OEM, Retail, Upgrade. One license per computer.

Q: How does Windows activation work?
A: Again, remember that Windows licenses are meant for use on 1 (one) computer. How is this enforced, you ask? Well, you will be given 30 days to 'activate', or verify, your license via internet or telephone. This only takes about a minute or so, and it's automatic. At activation your product key is linked (in Microsoft's system) to the unique set of hardware in your system. That means that you can reinstall and activate Windows on the same system using same product key as many times as you want.

You will only have activation problems if you attempt to install and activate Windows on a different PC, or if the hardware in your system changes significantly. In that case you would simply start reactivation via the telephone option (which will fail), and then you'll speak briefly with a Microsoft representative. We do this frequently on PCs that we repair for customers, and it generally only takes about 5 minutes.

Q: Is 64-bit Windows better?
A: Yes and no. 64-bit Windows allows programs to access enormous amounts of RAM (100GB+), compared with only 2 to 4GB for normal 32-bit windows. However, the average user doesn't come close to needing more than that; even the most demanding 3D games run fine with 1GB or so of RAM. Also, 64-bit programs aren't necessarily faster than 32-bit programs, and 32-bit programs run fine even if you have a 64-bit CPU (Athlon 64, Core 2 Duo, etc.).

The problem with 64-bit Windows is that 64-bit compatible drivers, utilities, and programs are either non-existent or new and buggy. Your favorite programs and games, as well as your printers, scanners and so forth may not work correctly, if at all. So unless you are running some industrial application that uses massive amounts of RAM, just stick with 'normal' 32-bit Windows. 64-bit Windows probably won't become standard for several more years.