The CC BHOList is the best tool you can use to determine what is harmful and what is not. To use the list, here's an example file listing:

Code:

Example Listing  O2 - BHO: NAV Helper - {BDF3E430-B101-42AD-A544-FADC6B084872} - C:\Program Files\Norton Antivirus\NavShExt.dll

Since it's in the O2 sector, the HJT Tutorial tells us that it corresponds to browser helper objects. Enter the number between the curly brackets - BDF3E430-B101-42AD-A544-FADC6B084872 - and enter it in the searchbox. Click Search, and it will tell you exactly what it is, where it comes from, the threat, and the filename.