dual boot - Splitting one partition into three

I bought a new laptop which had ubuntu installed in it and now I want to install windows8 on it along side ubuntu with dual boot, so I need separate partitions for windows, ubuntu and my data. I want to split my 443.76GB drive in to three drives, one for win8 OS and two equal size drives for data.

But before that I dont know what drive does the ubuntu OS is using for its files (i guess the 3GB drive ), should I increase its size ? Will I be able to use the ubuntu OS without any storage problems?

Please help me in a but of detail as I am new to linux, ubuntu.

Here is the current state of my HD...

1. Partition = /dev/sda1, File System = fat 32, Mount Point = , Label = Dell Utility, Size = 300MB, Used = 4.12MB, flag = diag




2. Partition = /dev/sda2, File System = fat 32, Mount Point = , Label = OS, Size = 3GB, Used = 1.84GB, flag = lba




3. Partition = /dev/sda3, File System = ext4, Mount Point = / , Label = , Size = 454.71GB, Used = 10.96GB, flag = boot




4. Partition = /dev/sda4, File System = extented, Mount Point = , Label = , Size = 7.75GB, Used = --, flag = --




5. Partition = /dev/sda5, File System = linux-swap, Mount Point = , Label = , Size = 7.75GB, Used = -- , flag = --

sudo fdisk -l
Disk /dev/sda: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders, total 976773168 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: 0x12c561d1
   Device Boot      Start         End      Blocks   Id  System
/dev/sda1            2048      616447      307200   de  Dell Utility
/dev/sda2          616448     6907903     3145728    c  W95 FAT32 (LBA)
/dev/sda3   *     6907904   960507903   476800000   83  Linux
/dev/sda4       960509950   976771071     8130561    5  Extended
Partition 4 does not start on physical sector boundary.
/dev/sda5       960509952   976771071     8130560   82  Linux swap / Solaris

Thank you.