To install hard drive on XP pentium 4 p.c

Hello, i have a 120 g.b. seagate hard drive that i need to retrieve data from,when i install it pc does not find connection,screen says boot from c.d, P.C.is pentium 4
with 20 g.b hard drive.....seagate H.D.120G, DOES WORK ,IT IS NOT DAMAGED HOW DO I GET IT TO WORK ..PLEASE HELP WITH STEP BY STEP INSTRUCIONS PLEASE