Hello all
I have phone with windows mobile OS. I would like to install linux-mobile on it. Which is the best system to use and if possible please give a brief how-to. By the way my phone is a dual-sim model.

Thanks in advance

At first, you have to make sure, that your phone actually can run linux. Normally you can not change an OS on a phone as easy you can do it on a pc.

You can definitely install linux alongside windows mobile. You just need to google for it. But your phone model should be supported by linux kernel. Currently the best option is Android and probably you will find one ported for your phone model.

No,we can not install Linux because it is a Windows-based mobile and PC as we can change the operating system easily, but here we can not do like all cell phones have a firmware installed base from Plant and embadded in mobile and can not be changed and deleted to be replaced by the same software.

You are right in some aspect. Traditional phones cannot be loaded with another operating system. But smartphones are designed like a computer having a processor, RAM, ROM, and disk space on flash and external & internal storage cards, have separate keyboard or virtual keyboard. Only problem is that the Operating System is loaded on internal ROM so as to make it run fast due to slow processor and less RAM.
This makes it very difficult to load another OS on the ROM replacing the original one. But it is occasionally done to upgrade the OS. Now with the availability of other OSes, specifically Android lot of people want it loaded on their devices. While Android and other mobile Linux OSes can run on these devices from external storage cards, they usually run very slow. The trick is to run a bootloader (haret.exe for windows phone) which shuts down windows and load Linux(another OS from storage card).
The best way to know whether your windows mobile can run Android or Linux is to install Haret bootloader and place a file default.txt in its directory with following line:
When you run the command haret.exe you should get your machine (mobile) name and a number other than 0 (its mtype). If the MACHMTYPE is 0 then your smartphone is not yet supported in the Linux kernel.

1. Search Web for Linux or Android for your device.
2. If your mobile is supported you will find the download link.
3. It should contain -
haret.exe (for your windows)- the bootloader
startup.txt - script to boot linux kernel
default.txt - additional boot parameters
zImage - The Linux kernel
initrd.tar.gz - ramdisk
rootfs.img.status - installation status of OS
rootfs.tar.gz (or system.tar.gz) - the root filesystem
4. Run haret.exe

The above will run the bootloader (haret.exe) which will load the linux kernel (zImage) with parameters in default.txt it will extract the rootfs image from rootfs.tar.gz into a virtual harddisk image - rootfs.img on your fat16 filesystem followed by installation instructions.

5. If above is successful you can create a separate linux ext2/3 partition on your external storage card and extract the rootfs.tar.gz into it to make your new OS run faster.

Where are you located? You make a very general statement that contradicts detailed answers from someone based in Mumbai to someone else who lives in India. What makes you think you know better? Do you have some facts to support your position?