Is nava actually nava.exe?
I typed "nava.exe" and "norton" into Google and got several hits that describe nava.exe as an unidentified worm or trojan.
I haven't found anything that will remove it other than an expert eye cast over a HiJackThis log.
click here and look under No2- the one you want is the "selfextracting zip".
In the Save box that opens, select your Desktop as the download location.
Double click the downloaded file and then click the "Unzip" button.
HijackThis will automatically be installed to this location: C:\Program Files\HijackThis.
Navigate to this location and double click the HijackThis.exe file.
Click the "Do a system scan and save a logfile" button.
A log will be automatically saved in the same folder as HijackThis.
Use Edit Copy/Edit Paste to post the log here- there's an 800 word limit per post on the forum, so you'll probably have to post the log a bit at a time.
Nellie2 is the Forum's HJT log expert, so wait for her response- she'll advise you about your HJT log.