Installing ubuntu using wubi limits your ubuntu drive into 30GB storage disk, not so bad if you're not really using as your primary OS. I, as a web developer and using ubuntu as my primary OS due to my current work, needed to have a larger storage disk but I don't want to backup my file and install ubuntu over again (traditional way). It's a hassle to backup files specially if I need the larger storage right away. So I've done some research and read a lot of articles if it is possible to just resize and extend the storage disk which was installed via wubi. And, yes, I found the solution that works for me.
First, download the wubi-resize_1.5b.sh. Save it on Downloads folder.
Next, open your terminal and type the following
cd Downloads sudo bash wubi-resize_1.5b.sh 50
The "50" on the code the number of Gigabits (GB) you want for your storage disk in your ubuntu. If you want it to be 100GB then you can change it to 100.
After hitting Enter on your keyboard then it will ask for the admin password. Just type your admin password.
It will take some time to create a new disk and base on my estimation, it took me 2 hours to create 50GB disk. So it's better to just leave your computer in a while. Make sure the charger is connected, you don't want to shutdown while in the process of creating the new disk.
When the new disk was created, you will go back to the Downloads directory. Now, shutdown to your ubuntu then log in to your Windows. Go to your ubuntu files then locate and rename the following:
\ubuntu\disks\root.disk to \ubuntu\disks\OLDroot.disk
\ubuntu\disks\new.disk to \ubuntu\disks\root.disk
If you're quite confuse of why it created a new disk instead of expanding the old one then let me explain it. We didn't literally expand our storage disk created a new disk and copy the old disk on it. If I must say, it's much more secure because in case that the expanding got an error you can just delete it and go back the old disk. So don't delete your OLDroot.disk until you're 100% sure that the new root.disk is working as it should be.