Can i the MS-DOS startup files onto a portable hard drive when i format my computers drive?

I have windows XP home edition. I'm formatting my hard drive. but i dont have a floppy. and my disc drive can't write onto discs. I need to format my computers hard drive, but i don't want to turn it back on and not have any files to boot off of. ....... This is a horrible explanation. but if you understand this. can you tell me how to get my MS-DOS files for windows XP onto an external drive while i format my computers hard drive.