Okay. I don't know whether this is success or failure. You decide for yourself.
I burnt 2 disks with 32 and 64 bit images of Ubuntu 11.04. But I did not even get the options menu ( Try Live CD, Install to disk, etc ) when I booted using them. All I got were black screens. ( I tried multiple times ).
Then I opened up Windows and discovered that I could install the 'Ubuntu installer' if I installed Wubi in C: drive. ( I don't remember whether I had tried installing Wubi in C: ). So my 2 CDs were wasted.
Anyway, I restarted my laptop and selected Ubuntu from the boot menu. And then.... again... A big black screen!
I tried using the Wubi installers of Ubuntu 11.04 32 & 64 bit versions. I also tried with the ISO file of the Digit customised Ubuntu 11.04. The results were same - static black screens!!
Now I am going to recheck if the Wubi installers are working on my other drives ( other than drive C: ).
Summary: I managed to install Wubi, but failed to boot using Ubuntu!