If the hole is large it can't be fixed - however a radiator repair specialist will be able to rebuild the radiator for you by fixing in a new core.
If the leak is tiny though, you can buy sealing liquids such as 'Radweld' from accessory shops. It works well enough for a while. Don't drive your car without water in it - the damage will be severe.
John
June 2008
I can answer this question...
How can I fix a hole in my radiator, 1997 Pontiac Grand Prix SE?