Without more information this is a bit of a guess but most likely I suspect you have configured Onedrive (with the same account) on both desktops and you have linked the Windows known folders to Onedrive. This will sync your desktop items to both desktops. You can read about it here: [https://learn.microsoft.com/en-us/sharepoint/redirect-known-folders
If it's not this can you please provide more information about your set up. For example, are you using Active Directory in your environment or how are you signing in to both desktops.