reformatting

hey,
can i refort a computer without having to use a cd-rom? because my cd rom can not be detected by windows, like when i turn on the computer when its loading it says its detecting it but when it loads and windows open its not there anymore. what can i do? i cant reformat it if my cd rom doenst work because i cant put in the cd. and when i try to repair windows by leaving the windows xp cd in the drive and start up windows it goes into a boot session. then i follow the instructions and once i hit repair it gives me a blank screen to type in codes and i dont know anything about dos. what should i do?