using two different os
 

How can you combine linux operating and other operating system to work on thesame system?

How? Depends on what you mean.
If you mean combine two systems into a single system; no, it cannot be done.

If you mean have two systems on the same computer; the hard-drive must be divided into partitions and the systems installed on separate partitions. Or one system can be on the internal hard-drive and a second system can be put on an external drive. I would advise doing some reading about partitioning and dual-booting before trying it.

I think you are trying something like dual boot... right?
If yes, check here.

Using GRUB 2.0 this can be achieved .
GRUB searches for all bootable images on the hard disk and asks which one to boot .

PS - You need different partitions for different images , otherwise you'll end up with sumthing wierd .
Also BACKUP IMPORTANT DATA before trying to achieve something.
Also read ,
http://http://www.dedoimedo.com/computers/grub-2.html

I see you're running XP. Here's briefly what you need to do for dual-booting with Linux:

1: Disable page file. Right click My Computer => Properties => Advanced => Performance: Settings => Advanced => Virtual memory: Change => check No paging file => click Set => OK => OK => OK

2: Reboot.

3: Defragment.

4: Resize. Use partitioning software on any live Linux CD or DVD. Leave unallocated space. Use actual installation CD or DVD to create and format Linux partitions.

5: Restore page file.

6: Restart with whatever distro.