pc crashed,previously no problems -running XP Professional, NTSC, message states acpi.sys file corrupted. screen blank -
how do I get new windows acpi-sys file in order to reboot without losing all info on pc

?
Have Windows XP installalation cd, inserted hoped to make "repair" but no luck. message montmgr.sys is corrupted
pc is HP Pavilion 850 mHz 312 ram 20GB old but no problems till now.
McAfee VirusScan suite installed.
What can I do!!!! obviously not experienced user (just retired!) can anyone help before I cart if off for repair - which I can't afford anyway!