Non-Genuine copy of Vista Problems

Hi,
My friend put on a non-genuine copy of vista ULTIMATE on my laptop. It kept
asking me to activate with the product key, but as this was not genuine i
didn't do anything.
My friend told me that it would just stop asking me for the product key, but
since i didn't activate my vista in time it has now de-activated and locked
me out of my computer.

What is the best thing for me to do? I have gone to a shop and they said
vista ultimate - was $700AUD to buy. This is to much money, i cant afford
that. I know i should not have done this but is there anything else i can do?

Please can anyone help me?

Erin