求助，安装ubuntu时无法识别空闲分区

[zhouphy5]

我是装得win7，现在要装个双系统。
好象是分区表问题，信息如下，求问怎么解决啊
ubuntu@ubuntu:~$ sudo fdisk -l

Disk /dev/sda: 750.2 GB, 750156374016 bytes
255 heads, 63 sectors/track, 91201 cylinders, total 1465149168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0xc17aaf7e

Device Boot Start End Blocks Id System
/dev/sda1 * 2048 411647 204800 7 HPFS/NTFS/exFAT
/dev/sda2 411712 313476344 156532316+ 7 HPFS/NTFS/exFAT
/dev/sda3 313476345 1465144064 575833860 5 Extended
Partition 3 does not start on physical sector boundary.
/dev/sda4 1328848605 1359805859 15478627+ 12 Compaq diagnostics
Partition 4 does not start on physical sector boundary.
/dev/sda5 313476408 805049279 245786436 7 HPFS/NTFS/exFAT
/dev/sda6 805049344 1328848604 261899630+ 7 HPFS/NTFS/exFAT
ubuntu@ubuntu:~$ sudo parted /dev/sda print
错误: 分区之间不能重叠。

[ljj_jjl2008]

等待那个头像是青蛙的高手。
这种问题，我不会解决。我都是备份数据，然后删光分区，再重新分区来解决的。