Even using the highest compression settings in utilities like 7-Zip, a 3GB Office installation file cannot be compressed down to 10MB. It is mathematically impossible to retain all the necessary code in that space. If a file claims to be Microsoft Office 2013 but is only a few megabytes in size, one of two things is happening:

Websites offering Microsoft Office 2013 highly compressed are rarely legitimate. Here is what you are actually downloading in most cases:

Provide a list of like LibreOffice.

: If your installation becomes corrupted, use the Online Repair tool found in the Control Panel under "Uninstall a program" > "Change" > "Repair". Free Alternative

Because these files are often custom-compiled by hackers, standard antivirus software may not always catch them immediately.