I have connected to a neighbor's wireless to ask

Its an adware you need to remove

Download Removal Utility for Mp3plugin.dll

I suggest XP in effect. I went in RUN - MSCONFIG then START table. You will find an entry for this DLL available. Uncheck box to select apply and start your PC again, then pop up on previous new beginning should have gone.

This will remove it.

or try it manually doing this:

Click Start> Programs> Accessories> Run> type: msconfig> Go to the Start Tab and look for a mywebsearch entry and untick it there. The above is a very easy and simple way to keep you away on Startup without becoming deeply involved in the processes of Vista, which if you're not experienced, you can cause more problems.