Sounds like you may be Infected. Try Birdy's advise below.
Download AVG Free AV. Update AVG & then scan your computer. There's a link for download in the thread below. See whether AVG fixes the problem for you.
tools/options
If that doesn't help, there are various other fixes (BFU, vundofix, system restore) in the threads below...there are different fixes to try as there seem to have been a few variations of this thing over time.
2 probs (LW keeps restarting & can't access options)
Starts on its own/ options folder won't open (possible fix)
installation aborts
WARNING: Viruses on network you should be aware of!
If you're still stuck, please go to one of these sites - they're specialists in malware removal & can help you!!
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Always make sure that you're using a good AV program. Keep it updated & use it to scan all files that you download, before you open them...hopefully you won't download infected files again