winxp home sp2

when booting my system I get an error advising ‘isapnp.sys’ is corrupt or missing. I have tried to use my setup CD but get a Code 4 error so I cannot user repair to fix the problem. I dont have a fat partition so I can get in to copy the missing files. I have also downloaded winxp setup disks 1to6 but that has not worked either. Any suggestions will be tried. Thanks