The POSReady servers are now offline. Microsoft shut them down in April 2019. However, the updates themselves are archived and can be manually installed via community repositories.
Windows XP's native networking stack (Schannel) is too old to understand modern security handshakes (TLS 1.2/1.3). This causes "Connection Not Private" errors even on official update servers. While Legacy Update already addresses some of this, a formal, automated module would solve the following: Automatic Root Store Sync windows xp legacy update
The standout feature of this tool is how frictionless it is. Previously, getting XP to update required manual registry edits, downloading standalone installers on a USB drive from a modern PC, and praying the file paths worked. The POSReady servers are now offline
: Run the setup. If nothing happens on Windows XP, you may need to unblock the file properties Windows XP's native networking stack (Schannel) is too