To "securely" wipe the current drive, boot from your OS X install discs and when the boot process has finished (it'll be asking you what language you want to use - ignore that for now), go to the Installer menu in the menubar and open Disk Utility. Select your hard drive and erase it - use the options for erasing to write all zeros. This can take a loooong time, btw. FWIW, the best way to secure the data is to either keep the hard drive and get a FireWire/USB2 external conversion kit (to use it as an external back up drive), or take a hammer to it. Even writing all zeros is not 100% secure.
Edit: Obviously you'll have backed up everything you need to another disc(s) first!
After installing the drive, boot from the installer disks again and use Disk Utility to format the disk. There is zero need to partition your hard drive unless you have esoteric demands such as constantly writing enormous DV files to and from the drive. Ultimately, every time I have partitioned a drive I have always ended up regretting it as invariably you'll end up running out of space on at least one partition.
However, if you did want to partition, when you format the drive using Disk Utility, you can choose to partition it then.
HTH
Edit: you can get an idea of what Disk Utility looks like and what it can do by opening it when booted in OS X - go to your /Applications/Utilities folder to find it. As you are booted off your hard drive when doing this, you can't use it to alter the boot disk in any way but you can use it to repair permissions of the boot disk. This is why you have to boot off the installer CD to be able to use it to erase, etc the hard drive.
Top
