To delete windows partition from ubuntu.

1) Command to see the partition
sudo fdisk -l
2) Mount the windows partition
sudo mount /dev/sda1 /mnt/
3) Look for the files and verify the data
ls -rlt
4)Then look for the available file system
sudo mkfs.
5)Create the new file system
sudo mkfs.ext3 /dev/sda1
6)Finally mounting the created partition
sudo mount /dev/sda1 /mnt/

To change the file system.
sudo vim /etc/fstab

To remove windows during bootup
cd /boot/grub/
sudo vim menu.lst
sudo grub-install /dev/sda


For referrence:
prakash@prakash-laptop:/boot/grub$ cat /etc/fstab
# /etc/fstab: static file system information.
#
#
proc /proc proc defaults 0 0
# /dev/sda3
UUID=38683652-4d42-4885-a18a-aa1fede0ca9d / ext3 defaults,errors=remount-ro 0 1
# /dev/sda1
UUID=C2C8BE9CC8BE8DE3 /media/sda1 ntfs defaults,nls=utf8,umask=007,gid=46 0 1
# /dev/sda5
#UUID=F0F6AC07F6ABCC62 /media/sda5 ntfs defaults,nls=utf8,umask=007,gid=46 0 1
# /dev/sda4
UUID=cc9c91ad-8b78-417f-9e49-beee5eeb1486 none swap sw 0 0
/dev/scd0 /media/cdrom0 udf,iso9660 user,noauto 0 0
# /dev/sda5
/dev/sda5 /home ext3 defaults,errors=remount-ro 0 1
# /dev/sda1
/dev/sda1 /data ext3 defaults,errors=remount-ro 0 1