That is very simple. If the only reason you hate the other OS is because it shows at startup, follow these steps. First, click start, and go to Control Panel. Then, click Performance and Maitenance. Then click System. At the very top of the window, there are different label such as, General, Hardware, etc. Click Advanced. Then click the lowest selection, the Startup and Recovery Settings. At the top, select the OS you want to boot, and tell it to not show the list of os's. Good Luck!
(NOTE: THIS IS HOW TO DO IT ON XP, IF YOU HAVE 2000, IT MAY BE DIFFERENT)