The only way sadly is to format, it is not possible to unistall an operating system to my knowledge

Think your going to have to back up your data, and format.

Someone post otherwise if I'm wrong, but if no one posts....

A full format would be the cleanest thing to do but if you don't want to full format...

Go in system properties in control panel and then go to Advanced. Then under Startup and Recovery click Settings. Then under System Startup click Edit. Remove the entry that you want to get rid off.
If you would want to get rid of Windows Xp Professional. remove the:

line.

Reboot the computer and you will not be prompted to choose an installation. Then simply delete the installation folder for the Operating System that you removed. For example if you had XP Pro installed on your d: partition and Home installed on c: and you got rid of Pro remove the d:\windows folder.

Dear colleage,
Thanks for your support. But let me forward you one solution forwarded from one of our (you and me) friend , a member in this site. His account name is "gemini4". I've used the solution he suggested and I problems are solved by my side

A full format would be the cleanest thing to do but if you don't want to full format...

Go in system properties in control panel and then go to Advanced. Then under Startup and Recovery click Settings. Then under System Startup click Edit. Remove the entry that you want to get rid off.

Quote:
[boot loader]
timeout=3
default=multi(0)disk(0)rdisk(0)partition(2)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(2)\WINDOWS="Microsoft Windows XP Home Edition" /fastdetect /NoExecute=OptIn
multi(0)disk(0)rdisk(0)partition(7)\WINDOWS="Microsoft Windows XP Professional" /noexecute=optin /fastdetect
C:\CMDCONS\BOOTSECT.DAT="Microsoft Windows Recovery Console" /cmdcons




If you would want to get rid of Windows Xp Professional. remove the:


Quote:
multi(0)disk(0)rdisk(0)partition(7)\WINDOWS="Microsoft Windows XP Professional" /noexecute=optin /fastdetect




line.

Reboot the computer and you will not be prompted to choose an installation. Then simply delete the installation folder for the Operating System that you removed. For example if you had XP Pro installed on your d: partition and Home installed on c: and you got rid of Pro remove the d:\windows folder.