I have a WIN XP SP3 notebook 32-bit PC well I plan Dual Boot with Linux (same PC). Now I have in my laptop two Partitions [XP]... May make a third partition and install Linux or, is needed to format again whole HDD and make two partitions ? The first is it difficult to get done ? If is done Linux can make use of everything in the PC apart from windows partition ?

If I want RUN LINUX from the CDROM ... any software run(not linux OS) must be installed on memory RAM, how this I do ?

Is needed to DELETE first the one partition(contents) and after split(make third) or this is optional I may keep may data/software ?
What we mean by saying "defrag you're windows partitions first" ?

If you are running from a Live CD/DVD, you won't have to touch the hard drive. The disc will boot and load the files to the memory automatically.

There is no reason to reformat. All you need is one partition for each operating system. If you want another partition, you can shrink the current partitions, and use the empty space for the Linux. You can then format that partition in something like ext3.

If your going to be using a Live CD, then there is no need to install anything onto the HDD, so no need to create another partition.

But if you do want to install Linux onto your HDD, then I suggest you take a look at Ubuntu. If you do decide to go down the Ubuntu route and you don't want to format again, I seriously recommend that you take a long at wubi (http://wubi-installer.org/). Basically you download and install wubi, just like any other Windows app and it creates a virtual HDD and when you boot up, you can boot into your Ubuntu install.

Or you could simply get a partition manager, create a new partition and install Linux in the new partition.