我找到答案了,在MS HELP中寫到:

If you run chkdsk without the /f command-line option on an active partition, it might report spurious errors because it cannot lock the drive. You should use chkdsk occasionally on each disk to check for errors.

If you specify the /f command-line option, chkdsk sends an error message if there are open files on the disk. If you do not specify the /f command-line option and open files exist, chkdsk might report lost allocation units on the disk. This could happen if open files have not yet been recorded in the file allocation table. If chkdsk reports the loss of a large number of allocation units, consider repairing the disk.

所以每個人的 Windows (不只是 XP) 應該都會這樣吧?