hi im new comer to linux.
i just gone through notes of booting but i couldnt understand what MBR is really for and GRUB and LILO.can anybody help ,is all this boot loaders?????

The MBR is the first sector of your boot disk: http://en.wikipedia.org/wiki/Master_boot_record
grub and lilo are boot-managers: They can let you select which (of perhaps very many) installed OSs you wish to boot.
lilo (linux loader) is considered rather old-fashioned, most distros are using grub now.

Just
[1] Backup your windows personal files. (Or, safest, replace your windows drive with an empty one, if you are really unsure, and terrified).
[2] Boot from a linux CD. Installation is quite easy now.
[3] Have fun.

And welcome to LQ!

Grub stands for Grand Universal Boot Loader. For what that's worth.

Your BIOS after checking out the hardware sends the heads of your boot disk to track one sector one, and does a read. This is where the MGR ( Master Boot Record ) is. The MBR directs operations from there. The MBR is an executable program, it takes control of the system, and goes and looks for the operating system files to load. ( Generic explanation ). This happens regardless of the OS installed.

Windoze writes its own MBR record when installed, and it will load only windoze. If you install a linux system, Lilo and Grub are the most common options to use. Either can be installed on the MBR, and therefore overwriting the windoze MBR.

During a linux install, the system will look for any other OS's, including windoze, and add a record to the menu, so you can choose to boot windoze, or linux. You can install multiple OS's and boot any one of them by adding the correct information to Lilo or Grub. If given a choice, pick Grub. It is ( in my opinion ) easier to maintain. Lilo and Grub have all the code you need to load most OS's.

Good advice above, back up any windoze stuff before begin installing linux. If you mess up the MBR, it can be recovered later. There are many ways to do that.

If you are going to multi boot, Windoze systems should be installed first. Then install what ever linux system you choose later. If you try it the other way around, the windoze install will re-write the MBR, clobber the Lilo or Grub code, and only windoze will boot. That is the way windoze is designed.

Hope this clarifies some things for you.

Well mbr is the master boot record.
grub (which stands for grand unified boot loader) and lilo(linux loader) are boot loaders.well what boot loaders do is that they recognize the operating systems installed in your computer and list them to you.now you are to choose which one to load.
lilo is now obselete.most of the distros like rhel5 use grub.its a powerful loader that recognises many o.s.
if you want to load windows and linux both,install windows first and then linux and its boot loader to mbr.If you install windows later its boot loader will be over written on mbr.its boot loader is not powerful enough to recognize linux installations and unfortunately you will not be able to boot linux
Enjoy.