ok vissu, STOP!
first of all, do yourself a favour and make a backup of all your important data and files. and by backup i dont mean copy it on the same hard disk! i mean copy it to another hard disk or burn a CD/DVD which is then kept safely away from your PC while installing ubuntu!
ya WUBI is probably safer although i havent tried it myself.
Start here
https://help.ubuntu.com/ its still for 7.04 but still good...
For installation/partitioning info, let me search and post some links...
ok, i got this link but it doesnt explain partitioning. you have to select "manual" partitioning. if you dont already have some free unpartitioned space on your hard disk you will have to shrink/resize existing
windows partitions to make space, which is risky. either run ubuntu thru WUBI or run it under vmware/virtualbox
https://help.ubuntu.com/community/GraphicalInstall
Got that link from the main link here
https://help.ubuntu.com/community/
@vissu: please post what is your current hard disk size, and what drives and sizes you can see under windows.
i can then try to explain what will show up under the ubuntu partitioner and what numbers/options to select.
for example, if you have a 80 gb hard disk and you have created 2 drives under windows of 40gb each, say C: and D:
then ubuntu might show them as "/dev/sda1" for C: and "/dev/sda5" for D:
then you might need to shrink sda5 by at least 4 GB to make space for the installation and linux swap.
you'll then create a "/dev/sda6" linux "ext3" file system (say 3-5GB) and select for formatting , and a "/dev/sda7" linux swap partition, say 1 GB.
the "mount point" for "/dev/sda6" linux ext3 should be root "/" and for sda7 swap should be the "mount point"
hope that helps, post more queries if you have them