Confusing partition options when trying to install Win 7

I'm trying to do a clean install of Win 7 on my 1545 with the 64 bit Win 7 cd that Dell sent and when it comes to choosing a partition I'm confused by what options I have. I get faced with 3 partitions the first one is like 70gb and says something about OEM at the end and it wasn't there when I did the clean install of Vista after receiving this laptop earlier this month. The other 2 partitions were there before the recovery one and the one where I previously installed Vista. Why is there now a 3rd one that mentions OEM and why is it taking up so much space?

I stopped my attempt at insalling Win 7 and came to post here when I saw the new OEM partition that I didn't create.....

 

You can just nuke them all and make one large partition if you would rather.

 

How would I do that? I'm not sure if I've ever deleted a partition or if I have I can't remember. This is the first laptop I've had that had a recovery partition, the other ones have always had just one large partition that I would just install whichever OS onto.

 

When you get to the part where you select where to install Win 7, go to Drive Options and then delete all of the partitions and format the one that remains.

Kind of like this,

http://www.techtalkz.com/gallery/files/1/Windows7-2008-11-04-14-55-10.jpg

This will clean everything off of your drive so make sure you have anything you want backed up.