I am facing the same problem, did you find any solution?

No, I haven’t found solution to this :(

This worked for me
 

1. Open regedit by clicking your start button and typing regedit and pressing enter. On Windows XP, Click Start, then run, then type regedit.
2. Find \HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\ and delete the key called DisallowRun.

theres no explorer when i open policies though

I'm sorry to hear that you're experiencing difficulties with installing Razer Synapse on your Acer Predator Helios 300. Error code 5 typically indicates that there are certain restrictions or permissions on your computer preventing the installation process. Here are a few steps you can try to troubleshoot the issue:

Run the installer as an administrator: Right-click on the Razer Synapse installer file and select "Run as administrator" to ensure that you have the necessary permissions for the installation.

Disable antivirus or security software: Temporarily disable any antivirus or security software you have running on your computer. Sometimes, these programs can interfere with the installation process.

Check User Account Control (UAC) settings: Adjust the User Account Control settings on your computer to a lower level temporarily. This can be done by following these steps:

a. Open the Control Panel.

b. Navigate to "User Accounts" and click on "Change User Account Control settings."

c. Move the slider to a lower level (e.g., "Never notify") and click "OK."

d. Restart your computer and try installing Razer Synapse again.

Ensure Windows is up to date: Make sure your operating system is up to date with the latest Windows updates. Updates often include bug fixes and improvements that could help resolve the installation issue.

Remember to re-enable any disabled security software and revert any changes made to User Account Control settings after troubleshooting.