Unless his CD-Rom isn't an ATAPI CD-Rom, boot the system off a boot disk. Press ENTER when asked, put the CD in. Type in R: or your CD Drive letter which I'm guessing is D: . Then type in cd\i386, press enter. then Type in winnt.exe press enter and there you go. This works for Windows 2000, 2003, XP and Windows NT.
Unless you are installing Windows ME/98/95, Boot the PC off a Floppy disk. Press ENTER when asked, put the CD in. Type in R: or your CD Drive letter which I'm guessing is D: . Then type in setup.exe , then ur free ;D.
Remember, this guide is if only he DOESN'T have an Atapi type CD-ROM OR His CD isn't self-bootable.