Hi woody43laker:
I have 32-bit Vista Home Premium SP2. KB971644 (Platform Update for Windows Server 2008 and Windows Vista) is not available for manual download from the Microsoft Update Catalog (see http://www.catalog.update.microsoft.com/Search.aspx?q=KB971644) but if I search my installed updates I can see that the all four of the updates bundled inside that platform update (KB971512 / KB971513 / KB971514 / KB960362) were installed on my system on 28-Oct-2009. Search your installed updates at at Control Panel | Programs | Programs and Features | View Installed Updates for those four updates (Note: search for the entire KB number, i.e., "KB971512" as shown below, not "971512") and see if any are already installed.
Extended support for Vista SP2 ended on 11-Apr-2017, but many Vista SP2 users have recently discovered that Windows Update failed to install all available updates before support for Vista SP2 ended. My first suggestion would be that you step through the instructions on page 1 of m#l's thread Updates not working, it has been searching for updates for hours and ensure your system has been fully patched by Windows Update. If you're missing any of the five Vista SP2 / IE9 security updates listed in STEP # 2 [KB3205638 (rel. 13-Dec-2016); KB4012583 (rel. 14-Mar-2017); KB4015195, KB4015380 and KB4014661 (rel. 11-Apr-2017)] those updates will have to be pre-installed before Windows Update can run to completion and patch your Vista SP2 OS to April 2017. Additional speed up patches will have to be pre-installed if you have MS Office 2007, MS Office 2010 and/or the MS Office Compatibility Pack SP3 installed.
If patching your system with all available updates doesn't solve your problem then post back and let us know if have 32-bit or 64-bit Vista SP2 and what software you are trying to install that reports that you still require KB971644. Fortunately, it appears that all four of the updates bundled inside KB971644 can still be downloaded separately from the Microsoft Update Catalog if you still require them. I've noticed a few recent threads posted by Vista users about about bugs in Kodi v17.x Home Theater installers that throw an error about KB971644 (see Windows - Kodi 17.1 Installation problem with KB971644 Vista x86) and you might be experiencing a similar glitch.
32-bit Vista Home Premium SP2 * Firefox ESR v52.3.0 * NS Premium v22.10.1.10 * MB v3.2.2
HP Pavilion dv6835ca, Intel Core2Duo T5550@1.83 GHz, 3 GB RAM, NVIDIA GeForce 8400M GS