BleepingComputer.com: Split Hard Drive 20/20

I bought my laptop (Acer Celeron processor, 512 RAM, 40 G hard drive) about a year ago. I didn't realize (and the guy should have told me) until too late that the hard drive is actually split 20/20, 20G on the C: drive and 20G and 20G on the D: Well, the C: is now getting full and the D: is virtually empty. The computer wants to use only the C: drive and things are slowing down. How do I get at the other 20Gs of space?
Thanks for any advice you could offer.

It depends on what's on the D: drive. If it's the recovery information, you'll be well advised to back it up before attempting to resize the disk. Then, you can use several different programs to resize/repartition the disk. My favorite is Acronis Disk Director, but it's not free - so I'll let others recommend a freeware solution.

Grab partition logic. It's free, and works pretty much exactly the same as partition magic.

Where would I get that?

I found Partition Logic. So basically what I need to do is delete drive D:? It beats me why it would have been set up that way with half of the space useless without a fix?
Thanks