The correct phrasing is:

KMS acted as a local, private activation server inside a company's own network.

Windows XP predates KMS by several years. The activation system in Windows XP is — a completely different mechanism that relies on a 25-character product key and a one-time online or phone activation with Microsoft.

Microsoft’s activation protocols (SLP, OEM, KMS, MAK) are version-specific. Windows XP uses an older activation technology called built around the 2001-2004 timeframe. The KMS protocol stack simply does not exist in XP’s kernel or system files.

—the digital lock Microsoft placed on the OS to prevent piracy. The Rise of KMS and Third-Party Tools In corporate worlds, Microsoft introduced the Key Management Service (KMS)

: Windows XP is no longer supported and is highly vulnerable to modern malware. If you are using it for retro gaming or legacy software, it is best kept or behind a robust hardware firewall. Microsoft Activation Scripts Volume License Keys

If the acronym started with a vowel sound (like "F" or "M"), you would use "an" (e.g., "an MBR activator"). But for KMS, it is .

If you're looking for information on upgrading, migrating data from XP, or securing an isolated machine, I can help with those alternatives.