Yes fix it in HJT and get rid of it if HJT doesn't also delete it.
BHO items (Browser Helper Objects), usually toolbars that you install to help you but many are installed without your knowledge and would be better described as browser hihacker objects. This may be used to serve ads or redirect to web sites of their choice, it is a browser hijack rather than a virus.
Google returns many hits on the dll file, this is just one of them
http://www.castlecops.com/tk3564-navshext_dll_navshext1_dll.html further links on that page
http://www.symantec.com/avcenter/venc/data/adware.systemprocess.html whilst it may be attempting to make you believe it is a nav shell or system file because of its location it isn't.
Whilst browsing or collecting email, etc. if you get infected then the malware by default inherits the same permissions that you have for your user account. So if the user account has administrator rights, the malware has administrator rights and can reap havoc. Wit limited rights the malware can't put files in the system folders, create registry entries, etc. This greatly reduces the potential harm that can be done.
Check out the link to DropMyRights (in my signature below) - Browsing the Web and Reading E-mail Safely as an Administrator.
