SATA I vs. SATA II

I just bought a new Seagate SATA-II hard drive to add to my storage space.  Right now it's recognized as a SATA-I HDD in BIOS, which leads to two questions.  1)Is it worth the effort to change it/is SATA-II that much faster, and 2)How would I fix it so it's recognized as SATA-II? 

I have a suspicion it's the jumpers in back, but the way my drives are mounted in my case it would be a bitch to take it out just to change the jumper and find out that's not it.  So what do I do, /comp/?

>>1
1. Take it out.
2. Remove the jumper.
3. Change the voltage switch at the back of your computer.
4. Put the jumper back.
5. Put it in.
6. Turn your computer on.
7. ????
8. Profit.