Check that you have administrator rights on the computer. Otherwise you will not be able to start and configure the required access setting. Very easy to check: click start, then open "control Panel". Start by double-clicking the menu "user Accounts". There will be listed all user accounts that are on the computer, and below the name will be "Administrator" or "Limited account".
The second thing to check is what file system is used. For example, your file is on the D drive, then open "My computer" and right-click the icon for the drive D. Select the menu item "Properties" — immediately opens a window with information about the logical disk. Look what is written opposite the words "File system". It is necessary that it was NTFS - it supports the separation of access rights. If the system is FAT32, you can format the logical drive in NTFS. Just don't forget an important point — formatting removes all data from the disk.
Suppose you have administrator permissions on the computer, and a suitable file system - NTFS. Locate the file that you want to protect. Right-click on the file icon and select "Properties". A window will appear with different tabs in which to find and select the tab "Security".
In the top half you will see a list of user groups that have access to this file. To prevent deletion of the file, change user rights. Rights are of different types, e.g., "Full access", "Modify", "Read", "Read and change", "Special permissions". To no one but you could not delete a particular file, you'll enjoy the read access — then the file will open, but you cannot remove it to change, damage (if it is text).
To differentiate access rights to the file, click "Edit". Will be almost the same window: the upper part lists the users that are in the lower categories of access rights. But with one difference: on the contrary rights are two columns - "Deny" and "Allow" - with the possibility of ticking off each line.
To prevent deletion of the file, click on the "Advanced" button and then "Change permissions". A new window opens in which uncheck the option "Inherit permissions". A window will appear with a warning about removing inherited permissions. Select the "Delete" button and confirm by pressing "Apply". Then repeat steps 3, 4 and 5, put a ban on full control and click Apply.