This is one of the least important problems you will ever have with Windows.
Autocheck looks for the "dirty bit" on your hard drive. This bit is set when Windows is started and gets reset when Windows is properly shut down. If an improper shutdown has occurred, the dirty bit is still set and autochk.exe invokes chkdsk upon startup.
You can ignore this problem, forever if so desired. If you suspect your drive has an error, run chkdsk /f and re-boot the machine. Chkdsk will run when the machine is restarted.
To repair the autochk error, put your XP CD in the CD drive and navigate to the i386 folder.
Copy autochk.exe back into your Windows system32 folder, over-write if needed, the error occurs also if the autochk.exe is no good in the computer.