You may have a problem with that 5Gig partition being your primary partition for your OS (operating system), and when you install new software on your computer it will try and install it in that 5Gig partition by default and you will run out of room.
Before you load up a bunch of stuff on the 70Gig partition you may want to delete it and get Partition Magic, then resize that 5Gig partition to the full size of your HD to avoid problems down the road.
You can
download a trial version of Partition Magic, but I'm not sure if the trial version has any of its features disabled. If that doesn't work you can buy the full version for about $50-$70. I'd try the download first. You'll find Partition Magic pretty easy to use.
Another option is if you have an extra HD laying around, and some HD imaging software (DriveImage, Ghost, etc.), and fill comfortable with removing HDs. You could transfer that 5Gig image to the other drive, then delete the 5Gig partition on your 75Gig drive, then transfer the image back.