It's hard to answer without knowing specifics of your workplace agreement or contract - but in my part of the world, accrued paid vacation time is refunded as basic salary if you resign. However, the company may be able to require you to take the equivalent days off during your notice period.
In you particular instance (now you've cleared up your question a bit more) - you should still be entitled to the annual leave you've accrued, and you've booked the time already. You might cause a bit of umbrage at leaving under these terms. You could offer three weeks notice, instead (assuming your vacation is one week) - giving two weeks work, still.
All of this does depend on what employment laws apply in your part of the world, and also what is specified in your contract - and has been mentioned in your contract, you should talk to HR about your situation.