[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINNT
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINNT="Microsoft Windows XP Professional" /fastdetect

把它存回boot.ini(文字檔)
如果只是這個檔案誤刪，很好解決，就怕...