When a computer's Windows XP installation is activated, Product Activation creates a hardware hash by analyzing ten pieces of hardware information in the computer:
- make and model of the CPU
- processor serial number (if available)
- total amount of physical memory
- graphics adapter
- IDE controller
- SCSI host adapter (if any)
any CD-ROM or DVD-ROM drives - serial number of the formatted volume where the operating system is installed,
- and the MAC address and other identifying information of the installed network card (if any).
As long as seven of the ten device or device categories report back as having been unchanged (what Product Activation describes as "votes" from each category), Product Activation will report the system as still being activated. Another important detail, but one that you don't see discussed much, is that after 120 days any hardware changes that remain within the threshold will become part of the new baseline for changes.
Example: If your computer has 1 gigabyte of RAM when activated, and you add another gigabyte, the hardware "vote" for memory will indicate a change. However, 120 days from that point, the hardware "vote" for memory will no longer indicate a change.
Perhaps you're thinking,
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"That's all well and good, but how do I know what Product Activation thinks has been changed or not?" Actually, there is a way to find out: a utility called XPInfo, from Licenturion, Inc. When run, it displays all ten hardware categories and indicates, via a checkbox, which categories are voting as "changed" since the last activation. You can use XPInfo to track how many votes are available and thus avoid an unexpected activation hassle.
Whenever possible, it's best to install any and all hardware that might be marked as changed by Product Activation before activating your PC. This way the changes will not be noted until you're finished adding or replacing hardware.
Note: If you're transferring a copy of Windows XP to another computer and 120 days have passed since the last activation of that particular copy on a piece of hardware, you can generally perform the activation automatically. But to be safe, it's best to do the activation by phone in the event you need to confirm that you're transferring an existing installation and not trying to cheat.
About the author: Serdar Yegulalp is editor of the Windows Power Users Newsletter, which is devoted to hints, tips, tricks, news and goodies for Windows NT, Windows 2000 and Windows XP users and administrators. He has more than 10 years of Windows experience under his belt, and contributes regularly to SearchWinComputing.com and SearchSQLServer.com.
More information on this topic:
- Tip: Back up and restore Product Activation in XP
- Topics: Windows XP installation
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This was first published in September 2006