Ls.exe + Iastor.sys errors in XP?

The computer was working fine.. but suddenly it switched off, and when I restarted it, it showed the error " ls.exe insufficient system resources " and when a key is pressed, it restarted.. I tried all the boot options like safe mode, last known configuration etc, but got the same error.. and when I tried to boot with the Win XP CD, it showed the error " Iastor.sys file is corrupted " .. What to do?