here's how to do it-
When you boot the LIVE USB for installation, you will get 3 options-
- Erase Windows xp and replace with Ubuntu 12.04LTS
- Install alongside Windows xp
- Do something else.
for your Requirement,you shold click on the 3rd option - Do something else.
That will take you to a partition table.
In the partition table you will see your partitions.(mostly the 1st one will be c drive)
but do remember to see the size of your windows partition (c) from windows b4 starting installation.because the size is the only thing that can help you recognise the c-drive when installing as you wont see labels like c or d there.
after you find out the windows partition,select it from the table below and click on delete..!!
That partition(and thus your windows) will be deleted.
Then select that unallocated space(which was the c drive earlier) and click on add.
Now,you can either directly make the complete partition as EXT4 for installing Linux or you can also add a SWAP partition.(It is always recomended to add a SWAP area for better performance but only if your ram is below 8gb)
If you select to add the SWAP AREA,do the following(otherwise go to the part below this sub-explaination starting from "NOW..")-
(After clicking on add)
Assign the space from that partition to SWAP AREA equal to double your ram.(e.g-for 1gb,swap area-2gb)
Select SWAP AREA from the file system drop down menu.
Select "Begining" in the partition positition dropdown menu.
Click on add.
Now, after you have added the SWAP AREA,do this-
Select the remaining "Unallocated space" and click on ADD.
Select Ext4 Journaling filesystem from the file-system dropdown menu.
Select "Primary" from the partition type drop-down menu.
Select the mount point as "/" from the mount-point drop-doen menu.
Select "begining" from the Positition drop-down menu.
Click on add.
After adding the paritions,from the table select the ext4 partition you see and tick in the corresponding chek-box(if not already ticked)
then Select INSTALL...