Yeah, unfortunately the standard "easy" partition manager doesn't let you wipe a current ubuntu install replacing it with the new one, instead it wants to install them side by side. You'll have to choose the manual option, and delete the 9.04 partition yourself, and tell it to make a new one with that freed up space. No biggie really, but if you are unsure you should definitely ask for help. I've accidentally deleted a few partitions I meant to keep with the Windows partition manager in my day, not cool. It's really not difficult, but since it's unfamiliar territory, help or a good tutorial is a great safety net. I think you'll like 10.04 and good for you keeping 9.04 and skipping 9.10. Trying to run 9.10 was 6 months of frustration. I decided to no longer waste my time with experimental releases and am going to stick with 10.04 for its full run. It's tough, as a long-time Windows user, to resist the urge to try out every new feature. I've gotta fight it

I'm not even going to update programs unless they are updated in the repositories now either.