The Inspiron 1545 can only accept dual-core Core 2 Duo or Core 2 Extreme chips. Core i3, of any generation, is a no-go. The good news is that it can take any Core 2 chip, which means you can install a 3.06 GHz T9900 or X9100 and it will work fine.
I'm typing this on a 1545 with a T9800 (2.93...