I dual-boot on this machine (160Gig drive), installed Xp to a 40gig partition, then on the remaining I set 12gig to root ( /), 2gig to swap, and the remaining to /home. 12 for root was not necessary, but with the space available, figured it was better to give it "breathing room"
if this sounds like what you want to do, boot from the cd, and step thru the setup/install, til you get to the partitioniong section, and choose the free space, and to create new partiton, and make the size what you like, mount it as /, and choose either ext3 or ext4 as the partiton type. I choose ext4, it is mostly the default these days, but ext3 is older and better known. ext4 is the new kid on the block, but seems quite fine from my experience.
Next, create another partiton for swap, choose swap as type, and make it about 2 gig. Any more is really a waste. Then choose whatever space is left over and make it your /home partiton, and ext3 or ext4 as you wish. Then just fill the rest of your details in and let it install. Just take your time and read as you go. You can even post from the livecvd if you feel nervous, and for real time answers, queries in IRC channel are also an idea. But basically, if you follow as i laid out above, you should be fine. Wish you the best. Cheers.