misaligned partition

After several installation process (of Debian 6.0 and ubuntu 11.04 Natty) I still have a strange problem: partition 4 is misaligned, although it doesn't really exists as you will see in the end from fdisk -l. Disk utility and sudo parted reported the problem. What shall i do? Get a boot CD with gparted and then?
During the installation processes it never wanted to create a sda4 it always went for 5...
The system is a new acer aspire 5750 laptop, 4GB RAM, Core i3 ant yes, a 320 GB HDD.

Thanks very much in advance

sudo fdisk -l
Disk /dev/sda: 320.1 GB, 320072933376 bytes
255 heads, 63 sectors/track, 38913 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x47367329

   Device Boot Start End Blocks Id System
/dev/sda1 * 1 1959 15728640 27 Unknown
/dev/sda2 1959 1972 102400 7 HPFS/NTFS
/dev/sda3 1972 14593 101382272 7 HPFS/NTFS
/dev/sda4 14593 38914 195354625 5 Extended
Partition 4 does not start on physical sector boundary.
/dev/sda5 14593 15571 7855104 82 Linux swap / Solaris
/dev/sda6 15571 38914 187498496 83 Linux

And
sudo parted
GNU Parted 2.3
Using /dev/sda
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) align-check opt 1
1 aligned
(parted) align-check opt 2
2 aligned
(parted) align-check opt 3
3 aligned
(parted) align-check opt 4
4 not aligned
(parted) align-check opt 5
5 aligned
(parted) align-check opt 6
6 aligned
(parted)