What tool do i need to open up a hard drive?

Its a western digital. Its dead, very dead, and I want in! I want to look at them platters, rip out the neodymium magnets inside... all that good stuff.

Looks like i need a screwdriver with a star shaped end. I went poking around the Internet and people say i need a torx screwdriver but i don't want to buy the whole set just for one screwdriver, so what size torx do i need?

A Torx #8 will do the trick fine. You can also use a #7 (a little looser in the socket, but it will work)
I use either one to open up WD Drives.

Ah the fun joy of opening up a HDD. Last time I did that was to do a window mod

Yeah that didn't last too long before the drive copped out but was cool.

I've had my luck with #8 dealing with a lot of electronics with a Trox.