no installation cd

i brought a second hand computer for the programes that were installed on it namely microsoft office 2003 pro , front page 2003 ,and a few other good ones about six months ago, off a reletive as they were moving over sea,s.
now the problem i have is i have decided it is time to reformat and i wanted to install office and front page on my computer and give the old one to my son to play around with ,BUTi have not got the install cds for office etc
is there any thing i can do, or do i have to reformat the hard drive and buy the programs again @$1500 plus dollars nz
i have the product keys
any ideas would be welcomed