I personally always do manual. Are you trying to dual boot or are you starting from scratch on the drive? IF you are starting from scratch I would manual it and set a partition for mount / (main linux partition) at 10-15 gigs, a SWAP partition at 1-2 gigs and then leave the rest in a last partition as everything else. This way your linux is separate from the rest of your things (such as word docs). If you are going to dual boot with windows but are willing to format the entire thing I would suggest installing windows first, formatting the entire drive, install windows on about 20 gigs since Windows is so inefficient and takes up so much for small things. Then I would suggest doing the same thing I said before on the remaining section. With the "extra" that is left over you can make a partition that is readable/writable and executable from both windows and linux....this is what I did. My split is 20 Windows, 18 Ubuntu, 2 swap and the remainder is mounted to /media/shared and is the one that is shared between windows and Ubuntu....