Windows 7 upgrade, clean isntall.

Upgrade Versions Windows 7

Let’s assume you have a machine with Windows installed on it. Maybe you bought it preinstalled from a PC maker. Maybe you upgraded a previous version (like XP to Vista or Vista to Windows 7). Maybe you built it yourself with a full retail license. Whatever. Now you want to upgrade. You have two options.

Windows Anytime Upgrade This option is exclusively for people who already have Windows 7 Starter, Home Basic, Home Premium, or Professional installed. This might be the case if you get a great deal on a new PC with a specific edition of Windows 7, such as a netbook running Windows 7 Starter or a notebook running Windows 7 Home Premium. You now you actually want a more advanced version, but the PC is preconfigured and can’t be customized. That’s where Windows Anytime Upgrade comes in. You can use this option to replace your edition with the one you really want, with the features you need.

It is very quick (10 minutes or less, typically) and does not require any media. You kick off the process from the System dialog box in Control Panel and then enter a valid key for the edition you want to upgrade to. You can purchase a key online or use a key from any upgrade or full edition of Windows 7. The starting version must be activated before Windows Anytime Upgrade will begin.

When the upgrade completes, you are running the new, higher version.

Retail upgrade Here’s the one that has caused all the recent controversy. A retail upgrade package is sold at a steep discount to a fully licensed retail product. The idea is that you are a repeat customer, and you get a price break because you already paid for a full Windows license earlier. Retail upgrades qualify for free technical support from Microsoft, even if the copy you’re replacing was originally supplied by an OEM.

So who qualifies for a Windows 7 upgrade license? The Windows 7 retail upgrade package says “All editions of Windows XP and Windows Vista qualify you to upgrade.” The same language appears on the listings at the Microsoft Store. Specifically:

Any PC that was purchased with Windows XP or Vista preinstalled (look for the sticker on the side) is qualified. This is true whether the PC came from a large royalty OEM or a system builder. You can install a retail upgrade of Windows 7 on that PC. You cannot, however, use the OEM license from an old PC to upgrade a new PC without Windows installed.
Any retail full copy of Windows XP or Windows Vista can serve as the qualifying license as well. If have a full retail copy (not an OEM edition) on an old PC, you can uninstall that copy from the old PC and use it as the baseline full license for the new PC.
Older copies of Windows, including Windows 95/98/Me or Windows 2000, do not qualify for upgrading. There was some confusion earlier this summer when a page at the Microsoft Store online briefly stated that Windows 2000 owners could qualify for an upgrade. This appears to have been a mistake.

So, who doesn’t qualify for an upgrade license?

If you want to install Windows 7 in a new virtual machine, you need a full license. A retail upgrade isn’t permitted because there’s no qualifying copy of Windows installed. (The exception is Windows XP Mode, which is included with Windows 7 Professional and higher.)
If you own a Mac and you want to install Windows on it, either in a virtual machine or using Boot Camp, you need a full license.
And if you want to set up a dual-boot system, keeping your current version alongside your new copy of Windows 7, you need a full license. You can evaluate the new OS for up to 30 days before activating it, but if you decide to activate and use the retail upgrade full-time, you have to stop using your old edition.

That last one always surprises people, but it’s right there in the upgrade license terms:

To use upgrade software, you must first be licensed for the software that is eligible for the upgrade. Upon upgrade, this agreement takes the place of the agreement for the software you upgraded from. After you upgrade, you may no longer use the software you upgraded from.

So, if you want to dual-boot on a system that is currently using a single Windows license, you need to have a full license for your new copy, not a retail upgrade.

As the table on the first page indicates, you can transfer a retail upgrade license to a new PC. This fact confuses some people. Remember that the PC on which you install the upgrade must have a qualifying license first. So if you buy a new PC with an OEM Windows license, you can remove your retail upgrade from the old PC (restoring its original, un-upgraded Windows edition) and install your retail upgrade on the new PC. This is covered in Section 17 of the Windows 7 license:

You may transfer the software and install it on another computer for your use. That computer becomes the licensed computer. You may not do so to share this license between computers.

According to wording on the retail upgrade media, “This [setup] program will search your system to confirm your eligibility for this upgrade.” It is, presumably, looking for evidence of a currently installed version of Windows XP or Vista.

Good Advice ^