DLL-Files.com Support says:
BitGuard, by PerformerSoft LLC, is a piece of software designed to prevent changes to various web browser settings, such as the home page and the search settings. BitGuard is often installed along with the Babylon Toolbar and the Delta Toolbar thereby ensuring that you won't easily be able to get rid of them. Since BitGuard.dll is detected as malicious by a large group of Antivirus software, it is not available for download.
If you are getting an error regarding this file missing, it is probably because your Antivirus has removed it to protect your system.
Uninstaller for BitGuard is available for download at Performersoft Website .