The partition where you install ubuntu is inside windows partition which is your host and it uses ntfs file system. So, you can't use chown, chmod and chgrp command to change the file permission.
Don't be dis-hearted just change one line in the file /etc/default/grub
From :- GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
To :- GRUB_CMDLINE_LINUX_DEFAULT="rootflags=umask=002,uid=1000,gid=1000 quiet splash"
After you make the changes save the file, you need to run
afterwards to update /boot/grub/grub.cfg
These changes give you full access to all your files on your host, including system files and it is very very dangerous, so make sure to stay away from system folders ie. your windows system and only try this when you really really need to
For reference you may visit Changing file permission on host in Wubi & How to change file permissions of host in Wubi?