If LW is starting up all the time & refusing to stay closed, sounds like you have a worm.

Try the easy fix mentioned at the end of point 2 here, it's worked for a lot of people.
WARNING: Viruses on the network you should be aware of

If that doesn't help, there are links to help sites below
Spyware Warrior :: Index
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SpywareInfo Forum FAQ - SWI Forums


Always make sure that you're using a good AV program. Keep it updated & use it to scan files that you've downloaded before you open them.