Dual boot Macbook Pro MD101 (Mid 2012), with OSX and Bootcamp windows and a FAT32 shared partition I tried this and my hard disk looks something like this:

Vikrams-MacBook-Pro:~ Vikramguria$ diskutil list
/dev/disk0
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.1 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                  Apple_HFS MACINTOSH H             250.3 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
   4:       Microsoft Basic Data SHARED                  167.9 GB   disk0s4
   5:       Microsoft Basic Data BOOTCAMP                81.0 GB    disk0s5


I cant see the option to boot into windows at startup. I guess I can have only 4 partition so that this works efficiently.
Can I just delete disk0s3 or will I have to start from installing windows?
Here I will assume you are using the BIOS/MBR legacy boot method for Windows. This means you are using a hybrid GPT. 

Idea 1:

You could delete disk0s3 so you only have 4 partitions. I would first copy the contents disk0s3 to a flash drive. The application needed to do this can be found here. It works with Lion through Yosemite. I have not yet tested with El Capitan.

The downside is that at some point an update to OS X will recreate the "Recovery HD" partition. So you will need to apply this fix again sometime in the future.

Idea 2:

Use gdisk (or some other tool) to create a MBR table that does to include disk0s3. In other works, you create a MBR table that contains disk0s1, disk0s2, disk0s4 and disk0s5. You then flag the fourth partition as active.

The downside is that other software (especially the Disk Utility application) will see this as a bug and may try to fix it so the MBR table contains disk0s1, disk0s2, disk0s3 and disk0s4. So you may need to apply this fix again sometime in the future.

Idea 3:

Change the order of your partitions so Windows occurs before OS X. In other words, you want diskutil list to produce the following output.

Vikrams-MacBook-Pro:~ Vikramguria$ diskutil list
/dev/disk0
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.1 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:       Microsoft Basic Data BOOTCAMP                81.0 GB    disk0s2
   3:       Microsoft Basic Data SHARED                  167.9 GB   disk0s3
   4:                  Apple_HFS MACINTOSH H             250.3 GB   disk0s4
   5:                 Apple_Boot Recovery HD             650.0 MB   disk0s5


The downside is this limits the use of the Boot Camp Assistant. The Assistant can still be used to create the installation media, but you probably will have to manually install Windows.

What is meant by manually install? This depends on whether you want to backup OS X and Windows to an external disk or just start over. Having copied the "Recovery HD" partition to a flash drive aids either option. Booting to the flash drive allows you to repartition the disk. Also, you can either backup/restore OS X to/from an external disk or reinstall OS X from the internet. I backup and restore Windows using a third party tool called Winclone. It works great but costs money.   

If you have additional questions, please post a comment below.