Hmm. First, I would scan it with an Antivirus - it seem's pretty suspicious to me. If that doesn't pick it up, use a nifty little program like Ad Aware 6.0 ... you can find it at www.download.com ... do a search for "Ad aware". Run it, because the .net extension sounds like it could possibly be a peice of Spyware. If it is, Ad Aware will get rid of it for you (and give your box a nice little spring clean too )
This is a bit a rough explanation but to my knowledge it is a file used when accessing paradox tables. It makes sure more that not more than one user is accessing the same information at the same time.