Written for Synergy 3 (v3.7.2) and Synergy 1 (v1.21.4), checked 3 October 2026.
Product: Synergy 1 and Synergy 3
Operating system: Windows
Solution
If installing or uninstalling Synergy 1 or Synergy 3 fails with error 2502 or 2503, give your user account full control of the Windows Temp folder, then run the installer again:
- Open File Explorer
- Navigate to Local Disk (C:\), then Windows
- Right-click on the Temp folder
- Select Properties
- On the Security tab, click Edit
- Select your user account (or Users)
- Tick Allow next to Full control
- Click OK, then OK again
- Retry the Synergy 1 or Synergy 3 installation
Why this happens
These errors come from Windows Installer. Whenever you install or uninstall a program, files have to be written to a temporary folder. If Windows is unable to write to that folder, you get these errors.
If this doesn't fix it, please get in touch with us.