I'd upgrade to Lion or Mountain lion if you have enough RAM (2GB or 4GB)
and your hardware supports it. They're better OSes and you'll be able to get iMovie and all the other iLife apps from the store.
Also, try contacting who you bought the laptop from.
Or, If you have a friend with a mac, copy the app from their computer using a flash drive. That would work just fine.
Thanks for your help guys, appreciate it. I just placed my order, and with luck will soon be making movies my family will cherish for centuries etc etc.