原因：
要在當前安裝了 Linux 的計算機上安裝 Windows XP（假定您要刪除 Linux），您必須手動刪除 Linux 操作系統所使用的分區。在安裝 Windows XP 的過程中，會自動創建與 Windows 兼容的分區。
解決方案（我只介紹我用的方案，帶有任何分區工具且可以自啓動光盤或U盤，你都可以。參考：http://support.microsoft.com/kb/314458/zh-cn）:
找一個Ubuntu9.04 desktop 光盤自啓動， 選擇第一個選項：Try Ubuntu without any change to your computer,進入圖形界面，選擇一個terminal。由於下面操作需要root權限，你可以參考我的上一篇blog：http://blog.csdn.net/dragonfly12/archive/2009/09/30/4620589.aspx
刪除分區工具我用fdisk. 下面是我的實際操作：
ubuntu@ubuntu:~$ sudo passwd root
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully
ubuntu@ubuntu:~$ su
Password:
root@ubuntu:/home/ubuntu# fdisk -l
Disk /dev/sda: 80.0 GB, 80026361856 bytes
255 heads, 63 sectors/track, 9729 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x624aa2e0
Device Boot Start End Blocks Id System
/dev/sda1 * 1 1318 10586803+ c W95 FAT32 (LBA)
/dev/sda2 1319 9729 67561357+ f W95 Ext'd (LBA)
/dev/sda5 3880 6804 23495031 b W95 FAT32
/dev/sda6 1319 1344 208782 83 Linux
/dev/sda7 1345 1466 979933+ 82 Linux swap / Solaris
/dev/sda8 1467 3879 19382391 83 Linux
/dev/sda9 6805 9283 19912536 b W95 FAT32
/dev/sda10 9284 9587 2441848+ 83 Linux
/dev/sda11 9588 9609 176683+ 82 Linux swap / Solaris
/dev/sda12 9610 9729 963868+ 6 FAT16
Partition table entries are not in disk order
root@ubuntu:/home/ubuntu# fdisk /dev/sda
The number of cylinders for this disk is set to 9729.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
(e.g., DOS FDISK, OS/2 FDISK)
Command (m for help): d
Partition number (1-12): 6
Command (m for help): d
Partition number (1-12): 6
Command (m for help): d
Partition number (1-12): 6
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table.
The new table will be used at the next reboot.
Syncing disks.
root@ubuntu:/home/ubuntu# fdisk -l
Disk /dev/sda: 80.0 GB, 80026361856 bytes
255 heads, 63 sectors/track, 9729 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x624aa2e0
Device Boot Start End Blocks Id System
/dev/sda1 * 1 1318 10586803+ c W95 FAT32 (LBA)
/dev/sda2 1319 9729 67561357+ f W95 Ext'd (LBA)
/dev/sda5 3880 6804 23495031 b W95 FAT32
/dev/sda6 6805 9283 19912536 b W95 FAT32
/dev/sda7 9284 9587 2441848+ 83 Linux
/dev/sda8 9588 9609 176683+ 82 Linux swap / Solaris
/dev/sda9 9610 9729 963868+ 6 FAT16
root@ubuntu:/home/ubuntu# fdisk /dev/sda
The number of cylinders for this disk is set to 9729.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
(e.g., DOS FDISK, OS/2 FDISK)
Command (m for help): d
Partition number (1-9): 7
Command (m for help): d
Partition number (1-8): 7
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table.
The new table will be used at the next reboot.
Syncing disks.
root@ubuntu:/home/ubuntu# fdisk -l
Disk /dev/sda: 80.0 GB, 80026361856 bytes
255 heads, 63 sectors/track, 9729 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x624aa2e0
Device Boot Start End Blocks Id System
/dev/sda1 * 1 1318 10586803+ c W95 FAT32 (LBA)
/dev/sda2 1319 9729 67561357+ f W95 Ext'd (LBA)
/dev/sda5 3880 6804 23495031 b W95 FAT32
/dev/sda6 6805 9283 19912536 b W95 FAT32
/dev/sda7 9610 9729 963868+ 6 FAT16
root@ubuntu:/home/ubuntu#
重啓電腦，現在把windows xp安裝光盤放入就沒有問題了。
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully
ubuntu@ubuntu:~$ su
Password:
root@ubuntu:/home/ubuntu# fdisk -l
Disk /dev/sda: 80.0 GB, 80026361856 bytes
255 heads, 63 sectors/track, 9729 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x624aa2e0
Device Boot Start End Blocks Id System
/dev/sda1 * 1 1318 10586803+ c W95 FAT32 (LBA)
/dev/sda2 1319 9729 67561357+ f W95 Ext'd (LBA)
/dev/sda5 3880 6804 23495031 b W95 FAT32
/dev/sda6 1319 1344 208782 83 Linux
/dev/sda7 1345 1466 979933+ 82 Linux swap / Solaris
/dev/sda8 1467 3879 19382391 83 Linux
/dev/sda9 6805 9283 19912536 b W95 FAT32
/dev/sda10 9284 9587 2441848+ 83 Linux
/dev/sda11 9588 9609 176683+ 82 Linux swap / Solaris
/dev/sda12 9610 9729 963868+ 6 FAT16
Partition table entries are not in disk order
root@ubuntu:/home/ubuntu# fdisk /dev/sda
The number of cylinders for this disk is set to 9729.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
(e.g., DOS FDISK, OS/2 FDISK)
Command (m for help): d
Partition number (1-12): 6
Command (m for help): d
Partition number (1-12): 6
Command (m for help): d
Partition number (1-12): 6
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table.
The new table will be used at the next reboot.
Syncing disks.
root@ubuntu:/home/ubuntu# fdisk -l
Disk /dev/sda: 80.0 GB, 80026361856 bytes
255 heads, 63 sectors/track, 9729 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x624aa2e0
Device Boot Start End Blocks Id System
/dev/sda1 * 1 1318 10586803+ c W95 FAT32 (LBA)
/dev/sda2 1319 9729 67561357+ f W95 Ext'd (LBA)
/dev/sda5 3880 6804 23495031 b W95 FAT32
/dev/sda6 6805 9283 19912536 b W95 FAT32
/dev/sda7 9284 9587 2441848+ 83 Linux
/dev/sda8 9588 9609 176683+ 82 Linux swap / Solaris
/dev/sda9 9610 9729 963868+ 6 FAT16
root@ubuntu:/home/ubuntu# fdisk /dev/sda
The number of cylinders for this disk is set to 9729.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
(e.g., DOS FDISK, OS/2 FDISK)
Command (m for help): d
Partition number (1-9): 7
Command (m for help): d
Partition number (1-8): 7
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table.
The new table will be used at the next reboot.
Syncing disks.
root@ubuntu:/home/ubuntu# fdisk -l
Disk /dev/sda: 80.0 GB, 80026361856 bytes
255 heads, 63 sectors/track, 9729 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x624aa2e0
Device Boot Start End Blocks Id System
/dev/sda1 * 1 1318 10586803+ c W95 FAT32 (LBA)
/dev/sda2 1319 9729 67561357+ f W95 Ext'd (LBA)
/dev/sda5 3880 6804 23495031 b W95 FAT32
/dev/sda6 6805 9283 19912536 b W95 FAT32
/dev/sda7 9610 9729 963868+ 6 FAT16
root@ubuntu:/home/ubuntu#
重啓電腦，現在把windows xp安裝光盤放入就沒有問題了。
至於爲什麼會這樣，是因爲硬盤引導分區的問題。這方面資料如果誰有興趣，可以google上搜去，我就不說了。