Can't install MS Office 2000?

After trying to tweak my lap top so it would run smother and faster I some problems. I reinstalled the software from the system recovery disks that came with it. I then did the MS updates. Loaded some other software. But every time I try to install MS Office 2000 I get an error message telling me "Windows files must be installed for your installation to proceed" "Insert ypur Windows XP Proffesional Service PAck 1 CD now. Service pack 1a is on the computer already. I dont have an SP1 CD. I have the recovery disks that came with the system. When I cancell out on the installation I get an error message that says Error 1933. The windows installed cannot update one or more protected windows files.
My system is a Pavillion ze4100. OS XP Proffesional, Pentium 4-M CPU 1.70ghz , 112 MB ram 20 gig hard drive.