Legacy Update Help
“Checking for updates” is taking too long
Windows Update has an infamous flaw: Checking for updates, especially for the first time, can be incredibly slow. This has been caused by the significant number of updates released by Microsoft over the years, and the effectively infinite number of configurations a Windows system can be in. To determine which updates are applicable to your system, Windows needs to evaluate many thousands of queries against your system configuration. Simply put, the age of the Windows version you’re using, and the number of additional Microsoft products installed on it, will affect how long you need to wait for Windows to check for updates.
This issue is especially apparent with Windows Vista and later, which significantly overhaul Windows’s “servicing” system. While the new servicing stack is far more reliable than in prior versions of Windows, it also exponentially increases the amount of work Windows must do to check for updates.
In 2016, Microsoft recognised the performance issues with Windows Update, and released servicing stack updates that dramatically improved, but still didn’t fully fix, the issue. Legacy Update installs these updates for you.
After installing Legacy Update, here is what you can expect:
Windows 2000, XP: Checking for updates for the first time may take up to 15 minutes.
Windows Server 2003/2003 R2: Checking for updates for the first time may take up to 30 minutes. Please be patient for this to complete. If you get the error message “External cab file processing completed with some errors”, simply try checking for updates again.
Windows Vista, 7, 8, 8.1: Checking for updates for the first time may take between 30 - 60 minutes. Please be patient for this to complete.
Office 2010: Having Office 2010 installed may cause checking for updates to never complete. There is a workaround available.
More technical details
Windows Update is a complex protocol, and applying updates is an elaborate juggling act to ensure only the correct updates are applied, and in the right order. Performance problems are inherent to Windows Update, and aren’t specific to Legacy Update.
When you check for updates, Windows and the Windows Update server compare notes on what’s installed on your system, and therefore which updates are applicable to you. Because there are thousands upon thousands of updates, this is a very long, slow process, heavily tied to your CPU’s single-core performance, and hard drive/SSD read performance. If you watch Task Manager while you check for updates, you might see svchost.exe, wmiprvse.exe, and TrustedInstaller.exe (on Vista and later) using up an entire CPU core. This is the Windows Update Agent evaluating the configuration of your computer so it can let the Windows Update server know which updates it needs to see. Old PCs can take tens of minutes to complete this stage, while a VM running on your modern laptop should fly through this in a few minutes. This process is heavily dependent on your CPU’s single-core performance.
While installing updates, you may feel a slowdown on lower-end PCs due to the volume of hard drive write activity. If you have a small amount of RAM in such a system, and a fairly slow hard drive, this can hurt the system’s ability to use the hard drive as swap/pagefile space. This will clear up once the updates finish installing.