first (note the space) from the Run box (Start>Run).
You will probably need your XP disk handy.
ChkDisk is another alternative (My Computer>highlight your hard drive>right click>Properties>Tools tab>Error checking. You will have to Reboot for ChkDisk to run.
If not successul, an XP Repair may be needed: you won't lose programs, applications, utilities, configuration etc, but still best to do a backup first.
If you do do a Repair, ensure that you select Repair and NOT Recovery Console (you have to select Install at least once, perhaps twice(?), before reaching the Repair option).