Replaced CPU won't boot up completely

Apr 6, 2018
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So I just got a new CPU cause my old Pentium 4 burned out my teacher gave me his CPU which was in his dell dimension 1100 and mine is a dell dimension 3000 and from what I've found on the web the CPU's are compatible with both computers. Anyway when I plug it in there is an orange light on faceplate and green on motherboard everything works on motherboard fan spins and no display. Please reply quickly need help thanks guys.