Reformatting a hard drive? I don't even want to get started on that. I reformatted my hard drive and it wasn't funny!
One question: How did you try to format it? Are you trying to go through the OS or are you trying to format in DOS mode? I don't think you would get a password if you were going through DOS mode.
Like the others said: Make sure you have all the discs that you need (i.e. sound card, video card, programs that didn't come with your OS, etc.) If not, you're in for pure "L" once you format!
And if you are getting rid of everything and starting over from scratch, you need to go in the BIOS and change your settings so when you restart your computer, your CD-ROM drive will be listed as the first place to look for the OS CD.
Have fun!