Interrupt without external help

Can someone tell me how to go to an interrupt in Arduino without attachInterrupt() which uses outside sources?I need this for a project of mine.

http://lmgtfy.com/?q=avr+interrupt

:)

I also need to be able to go to 4 interrupts.I have the Duemilanove,if anything matters.

Maybe this could help: http://www.arduino.cc/playground/Main/PcInt