dual boot - Ubuntu 13.04 not detecting Windows 7 during Install

I am trying to Install the latest Ubuntu 13.04 on my netbook but the installation is not able to detect any operating system installed on the machine. And asking me to either wipe out the whole disk or repartition it. I have already installed Windows 7 Strater, Android x-86 and Meego installed on my system.

During install it says " This Computer currently has no detected operating system"

Here is the output of sudo sfdisk -luS && sudo fdisk -l:

    Disk /dev/sda: 30401 cylinders, 255 heads, 63 sectors/track
Warning: extended partition does not start at a cylinder boundary.

DOS and Linux will interpret the contents differently.
Units = sectors of 512 bytes, counting from 0

   Device Boot    Start       End   #sectors  Id  System
/dev/sda1   *      2048    411647     409600   7  HPFS/NTFS/exFAT
/dev/sda2        411648 396642303  396230656   7  HPFS/NTFS/exFAT
/dev/sda3     396646337 488392064   91745728   f  W95 Ext'd (LBA)
/dev/sda4     457453632 474062084   16608453   7  HPFS/NTFS/exFAT
/dev/sda5     396646400 440594431   43948032   7  HPFS/NTFS/exFAT
/dev/sda6     440594433 441004034     409602  83  Linux

/dev/sda7     441004036 442028037    1024002  82  Linux swap / Solaris
/dev/sda8     442028039 457453567   15425529  83  Linux

Disk /dev/sdb: 1022 cylinders, 124 heads, 62 sectors/track
Warning: The partition table looks like it was made
  for C/H/S=*/255/63 (instead of 1022/124/62).
For this listing I'll assume that geometry.
Units = sectors of 512 bytes, counting from 0

   Device Boot    Start       End   #sectors  Id  System

/dev/sdb1   *        63   7864319    7864257   b  W95 FAT32
        end: (c,h,s) expected (489,135,30) found (208,254,63)
/dev/sdb2             0         -          0   0  Empty
/dev/sdb3             0         -          0   0  Empty
/dev/sdb4             0         -          0   0  Empty

Disk /dev/sda: 250.1 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders, total 488397168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x9c5506cc

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048      411647      204800    7  HPFS/NTFS/exFAT
/dev/sda2          411648   396642303   198115328    7  HPFS/NTFS/exFAT
/dev/sda3       396646337   488392064    45872864    f  W95 Ext'd (LBA)
/dev/sda4       457453632   474062084     8304226+   7  HPFS/NTFS/exFAT
/dev/sda5       396646400   440594431    21974016    7  HPFS/NTFS/exFAT
/dev/sda6       440594433   441004034      204801   83  Linux

/dev/sda7       441004036   442028037      512001   82  Linux swap / Solaris
/dev/sda8       442028039   457453567     7712764+  83  Linux

Disk /dev/sdb: 4026 MB, 4026531840 bytes
255 heads, 63 sectors/track, 489 cylinders, total 7864320 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xc3072e18


   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1   *          63     7864319     3932128+   b  W95 FAT32

I have tried this workaround but it is not working in my case. Any prompt help would be appreciated. I request moderators to not to immediately close this question even if they think it has been previously solved as those solutions didn't worked for me.

Thanks in Advance.

Edit: Now I have deleted the other two Operating systems namely Meego and Android-x86 but still no avail. The partition table now looks like this.

Disk /dev/sda: 30401 cylinders, 255 heads, 63 sectors/track
Units = sectors of 512 bytes, counting from 0

   Device Boot    Start       End   #sectors  Id  System
/dev/sda1          2048    411647     409600   7  HPFS/NTFS/exFAT
/dev/sda2   *    411648 396642303  396230656   7  HPFS/NTFS/exFAT
/dev/sda3     457453637 471796919   14343283  17  Hidden HPFS/NTFS
/dev/sda4     396644850 488392064   91747215   f  W95 Ext'd (LBA)
/dev/sda5     396644913 457450874   60805962   7  HPFS/NTFS/exFAT
/dev/sda6     471796983 488392064   16595082   7  HPFS/NTFS/exFAT

Please Help!!

Well I finally solved the Problem using the fixparts command... it needs gdisk utility to be installed.

Following are the commands I ran to make the install.

$ sudo apt-get install gdisk
$ sudo fixparts /dev/sda

and then press the key 'w'

Done!

For more information on what FixParts is and what it is for can be found at rodsbooks. FixParts has evolved from the same author's project GPT fdisk (which includes gdisk, sgdisk and cgdisk)