no ext power bad chip?


I got the Arduino Duemilanove 168 and I can't seem to get ext power to work. I believe it's the voltage regulator that has gone bad since I read 8v coming from it and I think it should be 5v. I can make the adruino power up from ext if i jump pin 2 and 3 but I don't want to fry my arduino so its better to check here for any help you can give

If you can give me any info what I can try or should I try and replace the chip?