A friend of mine recently bought an HP Pavilion DV8000 laptop that uses an A/C power brick with the following specs: 19vdc @ 4.7amps. Her previous computer is a Compaq Presario 906US, which uses an A/C power brick with similar specs: 18.5vdc @ 4.9amps. Both use barrel connectors with the center conductor being positive, and both adapters are marked 90 watt.

Does anyone know if the old power brick would work with the new computer, without risk of overheating, etc.? It would save having to buy a duplicate brick for the new computer in order to have one fulltime in the computer bag (which beats crawling under the desk to retrieve the original everytime she goes out of town).