It depends...
If it was the wrong polarity or had an excessive voltage, it can cause a LOT of damage, like blown circuits.
If that's the case, the motherboard and possibly the CPU need to be replaced, meaning it's beter to get a new computer. The drive is probably OK and the files on it intact. You should be able to install it in another computer. Some rare laptops can acomodate 2 drives, otherwise, you can install it in a desktop or in an external casing.
If it was the wrong model, then it may have damaged the connector. In this case, it can be repared.
Electro, April 2012
