Download the trial here:
http://www.sonycreativesoftware.com/download/trials/vegaspro
Download KeyGen here:
http://www.mediafire.com/?daesr7wus4muqb7
Once both are downloaded, open keygen and click the arrow, and look for Sony Vegas Pro 9, once you've found it, double click it. (DO NOT CLOSE KEYGEN TILL YOU'RE DONE)
Now click generate around 10 times..
Now click patch > My Computer > Local Disc (C:) (or whatever your hard drive name is) > Sony >
then click Sony Vegas Pro 9 and click OK
Now open the Sony Vegas trial, it will ask for your Serial Number it will say it on the keygen window.
It will always start with an I..
After that it will ask for some information, don't worry it won't be used for anything important.
Now it will ask for an Authentication code, it will have the matching auth code to the serial number on the Keygen window.
Once finished you will have a Full version of Sony Vegas Pro 9 for FREE (costs 399$ otherwise)