Who This Affects and What It Fixes
This article is for small-business employees who notice that the C:\Windows\Installer folder is consuming an unusually large amount of disk space. Certain applications may leave behind old installer files when they are updated rather than removing them, causing this folder to grow over time. The fix is to temporarily uninstall the offending application, which removes the associated files from the folder automatically.
Why This Happens
Windows stores installer files in C:\Windows\Installer so that applications can be installed, uninstalled, or repaired at any time. When an application is updated, those old installer files should be removed and replaced. However, some applications may leave previous versions of their installer files behind, causing the folder to grow larger than expected.
The file names in this folder are not descriptive, but examining the file signatures can help identify which application’s files are taking up space. If you suspect a particular application is responsible, do not delete the files directly — doing so can break the application or prevent future repairs and uninstalls.
How to Fix It
- Identify the application you suspect is leaving old installer files behind by reviewing the file signatures inside C:\Windows\Installer.
- Do not delete the files directly. Manually removing files from this folder can cause serious problems with installed applications.
- Temporarily uninstall the offending application using the standard Windows uninstall process (for example, through Settings > Apps or Control Panel > Programs and Features).
- After the uninstall completes, the associated installer files in C:\Windows\Installer should be removed automatically.
- If you still need the application, reinstall it normally after the uninstall is complete.
Need Help?
If you are unsure which application is causing the issue or you are not comfortable performing these steps, contact the ACS support team for assistance.
Common questions
Can I just delete files from C:\Windows\Installer to free up space?
No. You should never delete files from C:\Windows\Installer directly. Doing so can break installed applications and prevent them from being repaired or uninstalled properly. The safe method is to uninstall the offending application, which will automatically remove its associated files from that folder.
How do I know which application is causing the C:\Windows\Installer folder to grow?
The file names inside C:\Windows\Installer are not descriptive on their own. However, you can examine the file signatures to identify which application the files belong to. If you are unsure how to do this, an IT professional can help you investigate.
Will uninstalling the application permanently remove it from my computer?
The uninstall is only temporary if you choose. Once the old installer files have been cleared from C:\Windows\Installer, you can reinstall the application normally and continue using it as before.