Legacy Update: Get back online, activate, and install updates on your legacy Windows PC

This is a huge, long-awaited release I’m excited to share with you all 🎉

• By popular demand, the Legacy Update ActiveX control can now be installed on any version of Windows, from 2000 up to 11. This allows you to use the classic Windows Update website, in addition to the built-in control panel.
• Legacy Update now downloads all required components prior to restarting the computer, which solves issues with downloads failing on Wi-Fi and dial-up (!) after the restart.
• On 64-bit editions of Windows, Legacy Update now installs a native 64-bit version of its ActiveX control. This means you can use the Legacy Update website in both 32-bit and 64-bit Internet Explorer.
• Adds an option to enable Microsoft Update (updates for Microsoft products such as Office) on Windows 7, as the link to do so from Windows 7’s control panel no longer works. (Contributed by @renodr - thanks!)
• On Windows Vista, Legacy Update now installs a 2019 Windows Servicing Stack update from Windows Server 2008, which resolves an issue where installing Office 2007 or 2010 would cause Windows Update to stay “Checking for updates” forever.
• On Windows 7, Legacy Update now installs the SHA-2 Code Signing Support update, which solves some errors and saves time in installing updates after Legacy Update setup completes.
• On Windows 8, Legacy Update now installs a 2021 Windows Servicing Stack update from Windows Server 2012, which is more future-proof, and resolves the Servicing Stack Update failing to install in some cases.
• Fixes an issue where Legacy Update could unnecessarily reinstall Windows 8.1 Update 1. (Contributed by @renodr - thanks!)
• Fixes the LegacyUpdateTemp user sometimes not logging off correctly after the setup completes. (Contributed by @renodr - thanks!)
• Fixes the downloader failing on original Pentium systems. (Contributed by @renodr - thanks!)

A massive thank you goes to @renodr for a good chunk of the features/fixes in this release, and some features that will be coming in Legacy Update 1.8.

This release will feel very minor on the surface, but I put a bunch of work into improving the codebase.

• Switches the file downloader library to one that seems to be a lot more stable, and reliable in every condition - slow internet, insufficient RAM, internet faster than your RAM/hard drive can keep up with, etc. It is also able to reconnect and continue if your connection drops during a download.
• Refactors the ActiveX control from the hefty Microsoft MFC framework to the lighter-weight ATL framework. This brings down the file size of the DLL.
• Uses more efficient compression on the installer (LZMA rather than Gzip), bringing the download size down even further.
• Improves error handling in the ActiveX control, so that in the unlikely case of the Legacy Update ActiveX control itself failing to do something, more useful error information will be displayed.
• Fixes installing Service Packs on Windows Vista/7 again - this was supposed to be fixed in 1.6.1 but I created another bug in the process.
• Fixes the LegacyUpdateTemp user lacking administrator permission on non-English installs of Windows, causing a "log on as an administrator" error after Legacy Update setup automatic restarts.

The massive changes in this release seem to have tripped up the exceptions Legacy Update was receiving from antivirus vendors. Currently, Microsoft and BitDefender are triggering false positives. This should be corrected soon, once both companies respond to my tickets. (Update: Microsoft Defender false positive resolved.)

• Fixes Windows Vista/7 Service Packs not installing due to a missing .exe extension on the file Legacy Update downloads.
• Legacy Update setup now requests Windows to not put the PC to sleep while it's running.

• Fixes “The parameter is incorrect.” error when launching Legacy Update from the Start menu or Control Panel on Windows 2000 and XP 32-bit.

• Fixes the Legacy Update proxy server not being configured correctly, causing connection errors (error 80072EFE) when checking for updates on Windows 2000, XP, and Vista. Fix contributed by @renodr - thanks!

• Legacy Update now configures .NET Framework to use the Windows SSL configuration. This ensures programs built on .NET can access the same websites you can access in Internet Explorer.

• When running on a processor that doesn't support later Windows Embedded POSReady 2009 updates (Intel processors prior to Pentium 4/Pentium M, and AMD processors before Athlon 64), Legacy Update will now disallow enabling POSReady updates. See #89 for more information.

• When downloading Internet Explorer 6 SP1 for Windows 2000, Legacy Update now downloads the installer for your language directly from Microsoft. Previously, this would download an English-only copy of the IE6 installer hosted by Legacy Update. Huge thanks to @stdin82 for finding live IE6 download links on the Windows Update server.

  This change was also able to be backported to earlier versions of Legacy Update. A separate “Internet Explorer 6 Downloader” helper will be launched when running from these versions.

• Fixes the Legacy Update proxy server not being removed on uninstall on Windows Vista, and Windows Update shortcuts not being restored on uninstall on Windows XP x64/Server 2003. Fix contributed by @stdin82 - thanks!

• General code cleanup: Rebuilt Windows version checking logic from scratch to avoid annoying edge cases in the NSIS WinVer.nsh library Legacy Update was previously using, and consolidated repetitive code for patches.