you cannot legally download windows xp pro. If you do not own a windows license, use Linux instead.
Ubuntu and Fedora are operating systems based on the Linux kernel. There are many operating systems that use the Linux kernel (sometimes these are called "Linux distros"). I recommend either Fedora 17 or Ubuntu 12.04.
Hello, my laptop asking me insert system disk which i don't have. Where i can download a system disk for windows xp pro? Thanks
That usually means you left a floppy disk in the drive (if the laptop is that old), or that the hard drive has failed or become corrupt. First check for a floppy disk, and if that is not the problem then you need to reinstall XP or another OS like nhasian suggested. If reinstalling an OS fails then you might need to replace the hard drive first.
Depending on your computer you may have a recovery option available. It will wipe out all your installed programs and revert to the original settings. Chances are you may be saved by a system restore. As you boot keep tapping the f8 key and you should come up with a menu you have an option to pick safe mode. Choose that then pick no, you hopefully will be able to pick a restore date prior to the problem.