|mmm - These sort error messages can be a real pain...|
Have you made any changes to the system prior to the problem(s) arriving?
Have you any restore points prior to the present problem's arrival?
Can you boot up "normallY at least; and/or can you also boot into safe-mode OK?
Do you have an XP cd - not a recovery disk, but an actual installation disk; and one that matches your type of OS installation (OEM or Retail accordingly).
You might also try running XP sfc routine (see link below) - as this will check for corrupted Windows files and (hopefully) repair them...
Is this a laptop or desktop/tower system?
Can you access memory sticks and clean them individually? Use a soft pencil eraser to do this, and ensure all "debris" is wiped off the edge connectors before re-installing the sticks. Remove all power (battery included if a laptop) before removing RAM...; ensuring that the mains power cord is NOT attached and "live".