- Windows Serial Number: This is the "Product-ID" displayed e.g. in Windows 7 in System Information dialog when you press [WinKey+Pause] key combination and has the format e.g. XXXXX-OEM-XXXXXXX-XXXXX. Please note: This is NOT the 5-part "Product-KEY" (which can be changed by the user)!

- Persistent: This means whether it remains unchanged during the whole lifetime of a specific Windows installation.

- Unique: This means that there are not 2 computers having the same Windows Serial Number. How is this handled with enterprises having a Windows Volume License, where they get one Windows install disc from which all computers in the company are installed? Do they have all the same Windows Serial Number?
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☠ MASQ ☠Commented:
Quite suprised not to find this answered already.

Just to recap - although your question wording implies you've already understood this bit ...

- Product Key is the activation key which is supplied with Windows either on a CoA sticker on the case for OEM installs, included in the Retail packaging or supplied by Microsoft either as a vluome licence or through a subscription channel such as MSDN.  Apart from stickers (where the Key displayed may not be the actual activation key) this is invisible to the user once the system is activated & needs decryption from the registry to recover.

- Product-ID This is a string representing the installation media used and can be used in a support role to identify how Windows was originally installed on a PC. So for example Microsoft may redirect you to the manufacturer of an OEM system for support having identified this from the Product-ID

Successful activation depends on the Product Key and Product ID matching so a volume license Key shouldn't activate an install with a retail Product-ID.

Product IDs are persistent for the same hardware and this ia particularly true for OEM installs on manfacturer's hardware but they are not unique - consider for example multiple installations on identical PCs using the same volume key.

All Product Keys are unique but some are used for multiple installs.  Product Keys are persistent unless an Anytime Upgrade is used where the key is replaced with the upgraded Key.

Validation of installations considers the Product-ID as well as the Product Key so multiple installtions of a retail key will be flagged but multiple installations of a volume key will not.

Was that the kind of information you were looking for?

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MASQ covered Product ID and Product Key well. What's important to note is that neither of them are a "serial number" and thus were never intended to be unique.

An alternative would be to look at either the Security ID (SID) or Client Machine ID (CMID) Windows generates for each install. These should be unique, but if a drive was cloned and not properly sysprepped, it's possible for two machines to have identical ones:

If you want to uniquely identify a PC, you could extract the serial number from the BIOS. Since this is a serial number of the hardware, it will be unique to that PC:

Another possibility is to grab the MAC address of the integrated Ethernet controller of the PC.
☠ MASQ ☠Commented:
MACs on Ethernet controllers aren't unique either and it can be a real pain if you unexpectedly find yourself with matching IDs (Try Googling "the same MAC address"  for some tales of woe :))

I concentrated on Product-ID as you equated this with "Serial Number" in your question.
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PeterDelphinAuthor Commented:
@ marsilies After executing "wmic bios get serialnumber" from an administrator cmd, I got the string "SerialNumber" (without quotes) as response!?
PeterDelphinAuthor Commented:
@MASQ Thanks for your competent answer. As I understand your answer to my question, there is a chance that a company could have several computers with identical hardware components having the same Windows Product ID? How would Microsoft itself in this case distinguish these computers?
I just tested the command "wmic bios get serialnumber" on my PC, and Got back two lines.

The first line was the string  "SerialNumber" .

The second line was the serial number of the PC.

I guess it's possible that a particular computer may not return the serial number from the BIOS, especially if the BIOS doesn't have the serial number stored in it.
☠ MASQ ☠Commented:
Corporately Microsoft doesn't distinguish between them - although if identical images are being distributed then locally the organisation should ensure unique identities to prevent networking conflicts (eg the security identifier or SID) but Product IDs and Keys aren't used to do this.
☠ MASQ ☠Commented:
Wow, I'd forgotten about this, thanks for finally closing it - sorry you didn't think the answer deserved a better grade but I gave it my best shot.
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