From your post it is not clear whether your tried to install a new operationg system (probably XP) over the old one, or to a new formatted partition.
Because if first is true - you definitely wasted your time replacing hardware.
Supposing your XP cd is bootable, boot from it, when it detects existing windows install do:
1) if you have precious data on prev. winxp partition - refuse
to repair existing installation when prompted, and set up new (second, third...) partition, format it to ntfs, and let the windows install there.
2) if No precious data on the drive refuse
to repair existing installation when prompted, - just delete all existing partitions, re-partition your drive as you want (say, c: 10gb, d:20gb, e:30gb), and re-format your new boot partition to ntfs (probably c