First make sure that you have logged into an administrator user account.
If you have logged into a standard user account you will not be able to save any file in the C drive.
There are possibilities that the security software installed on the computer is blocking the file saving on the C drive.
I would suggest that you disable the security software installed on the computer and check. Important: Antivirus software can help protect your computer against viruses and other security threats. In most cases, you should not disable your antivirus software. If you do have to temporarily disable it to install other software, you
should re-enable it as soon as you’re done. If you are connected to the Internet or a network during the time your antivirus software is disabled, your computer is vulnerable to attacks.
Also make sure that you have not set any parental controls on the computer.
If the above step fails then check if it works in the safe mode.
Steps to boot to Safe mode with networking
1. Restart your computer if it is powered on.
2. Tap the F8 key after your computer initially powers on.
3. Once you see the Advanced Boot Options menu you can stop tapping.
4. Use the up/down arrow keys to highlight your selection.
5. Select Safe Mode with Networking and press Enter.
6. You should see drivers loading, and then Please wait.
7. You should then be at the Welcome Screen.
8. Logon to your computer using an account with Administrator privileges.