I think Firefox would normally open to your default Downloads folder. You can check on that setting on the Settings page:https://support.mozilla.org/en-US/kb/where-find-and-manage-downloaded-files-firefox#w_change-where-downloads-are-saved

If you notice this across your applications, that they want to save videos or other types of content in OneDrive instead of your Documents or Downloads folder, there is a system setting for that. In Googling around, it could be this one:

• In the Windows 11 search box, type or paste storage settings and click the main result, which should open the Storage Settings control panel
• Scroll down and click on "Advanced storage settings" to list specific categories
• Click "Where new content is saved"
• If there is a category which points to OneDrive, change it to your C drive (or if you prefer a different local drive, that drive)

I really appreciate your efforts to solve my problem, and I tried your suggestions, but I still have the same problem.

I just re-read your original question and you mentioned your virtual desktop. Is that something different than the user profile desktop at

• %userProfile%\desktop
• C:\Users\<username>\Desktop