unrevoked3 recovery reflash tool, v3.22
Here is the unrevoked website. If you're using a Windows PC, download the HBOOT files and install them. When you click on the above link, go to "More Info?" to learn about the HBOOT files. Other than that, just make sure to follow the instructions for unrevoked. Also, you may want to do research to see what you can do AFTER your phone is rooted. Just having a rooted phone doesn't mean anything if you don't know what it can do.