Don't know what happened, but you appear to have posted the same thread twice. If you click the red triangle at the top-right of the thread, you can let the mods know and they'll delete the thread you're not using.
As for all the stuff on your computer, you're correct in assuming the more you install the more it can impact on your computer's performance.
Go to Start>Control Panel>Programs>Uninstall a Program and uninstall any program you don't use.
You can also use a third-party uninstaller such as Revo Uninstaller, which can be downloaded here: http://www.revouninstaller.com/revo_..._download.html
Just download the free version unless you feel inclined to buy Revo Professional. Revo will do a better job of tidying up leftover remnants of uninstalled software.