I want to install Ubuntu for the first time in my notebook, is this necessary to partition my whole hard disk to install Ubuntu or just the C drive or any one (like installing windows 7 or others)? I don't want to lose all my data...
The installer provides alternative ways to install Ubuntu. It can resize an existing Windows partition and install it along it allowing you to dual-boot. Or it can use the whole disk in which case it will use one partition for system and data. Or you can specify partitions manually.
If you want to divide your "system" and "data" on Ubuntu on separate partitions similar to the C: and D: paradigm on Windows, you can do that by making two partitions. Both need to be Ext4. The "system" one needs to be larger than 10GB, 20GB is probably enough for absolutely anything whereas 15GB should be a good average. The rest of the space goes for the "data" partition. Once you have the two partitions, use manual partitioning and tell the Ubuntu installer to use the "system" one at the "/" mount point and the "data" one at the "/home" mount point.
Note that once you to tell the Ubuntu installer to use manual partitioning you have to also specify a Swap partition. That can be any partition with larger size than your physical RAM and type swap. Some people recommend double the RAM but that could be an overkill nowadays. Once you have a swap partition you have to tell the Ubuntu installer to "Use it as Swap".
That's all. :)