You can (could?) use your Flex Builder 2 serial number with Flex Builder 3 (beta 1 or beta 2 only but not beta 3 or later).
But the short answer to your question is no, you won’t be able to use your Flex Builder 2 serial to “unlock” the Flex Builder 3 release. You’ll need to purchase a new license. The good news is that the pricing is very good.
For more information, see Ted Patrick’s blog entry: http://www.onflex.org/ted/2007/10/flex-3-beta-2-lower-price-flex-builder.php

Peter

I dont know if this may sound silly, but

Is there any chance by which my flex builder 2′s license will work with flex builder 3 too??

Or should I have to buy one. I had already spent some omey for fb2 license :-(

Please help

venkat