If you know the name of the File try searching for it with Windows. If not you will have to search mainly based on the date and file type.

Note with Windows 7 it initially searches in a single location but then gives an option to expand the search. See

• http://windows.microsoft.com/en-US/windows7/products/features/windows-search
• http://windows.microsoft.com/en-GB/windows7/Advanced-tips-for-searching-in-Windows

If "Open" and "Open Containing Folder" in the right-click context menu in the Download Manager window are grayed then that means that the file is no longer in the original download location and they may have been removed by Anti-virus or cleanup software.

It is possible that your anti-virus software is corrupting the downloaded files or otherwise interfering with downloading files by Firefox.

• http://kb.mozillazine.org/Unable_to_save_or_download_files