One way to clean it up if you don't want to remove or delete everything and don't like how it looks like that is to make the menu scrollable. This could be done via:
Right click on taskbar>Properties>Start Menu>Customize>Advanced
Scroll down the list and check Scroll programs
Other than that, you can go delete things you don't want off from there;
Or, group your programs such as they would look like:
START>PROGRAMS>Music Players>Winamp, Win Media, Itunes, etc.
------------------>Instant Messengers>Aim, MSN, icq, etc.
etc.. whereas before you wouldn't have them all grouped, but all individually taking up a slot on the menu.