Hmm...
I'm no expert on this (rarely affected by such things) but off the top of my head -
explorer is
not internet explorer.
One is your hm...gui perhaps..your windows and such.
The other is your browser. (which I do NOT recommend using as your standard browser in the future. nor Netscape. Look into Firefox or Opera once you get this sorted).
Sounds like you have a hijacker, check the sticky at the top of this forum for all the progs you can run to clean up your system.
Depending on the results/performance after, you may simply be better off doing a format c: (perhaps have a more puter literate friend help you with that?).
Good luck!
//edit: what version of windows you running?
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Therell be days/When Ill stray/I may appear to be/Constantly out of reach/I give in to sin/Because I like to practise what I preach