Help choosing a distribution!

Hi, I'm a serious newbie to any non-Windows OS. I have a Lenovo S10 netbook which came with Windows XP. I had the standard problems with Windows and decided to try out Ubuntu Netbook Remix 9.10. I like the OS quite a bit as everything worked right away, but it is running much slower than XP did.

Some examples:
- I'm running a FRESH install (this morning) of Ubuntu NBR 9.10. It is taking 3-4 minutes to simply uninstall a unwanted game through the Ubuntu Software Center. I have no other programs running!
- Firefox is absurdly slow, with no extensions installed at all.
- Clicking the "Go Home" button to reveal the deaktop with the Ubuntu NBR laucher shortcuts takes 20-30 seconds. I've added a regular gnome main menu button to the panel and even opening that takes 5-10 seconds. This kind of stuff ought to be instant. It was with XP, at least.

My Lenovo s10 netbook has a 1.6 GHz Intel Atom processor, 512 MB Ram, 80 GB hard drive. It does not have Bluetooth, but does have a webcam.

I'm looking for either
(a) help figuring out why Ubuntu NBR 9.10 is running so poorly on my machine
(b) help choosing a different Linux distribution that will suit my needs.

more on (b): I've read about many of the different distributions. I know that I don't need anything that looks fancy or has lots of built-in features. Ubuntu has both, and it seems to me (as a newbie who, at this point, is frightened and confused by the command line) that it is very hard to trim it down. I just want a basic system that will run smoothly on my netbook, allowing me to browse, play music and video files, and use OpenOffice or similar applications.

Any advice would be very much appreciated!