desktop effects could not be enabled

when i was trying to change desktop background and select in that visual effects as normal or extra so got the folling error

desktop effects could not be enabled

Do you have the display driver installed? I had the same issue, where it was fixed by installing the driver. I was having Nvidia chipset.

Do you have the display driver installed? I had the same issue, where it was fixed by installing the driver. I was having Nvidia chipset.

> select in that visual effects as normal or extra

Doesn't sound like a current version of Ubuntu. Which Ubuntu release is it?
The list tells which release still has support or is EOL.
https://wiki.ubuntu.com/Releases

You've assigned the question to desktop-effects package, the latest was for 8.04 where desktop release is EOL.
http://packages.ubuntu.com/hardy/desktop-effects-kde

The message
> desktop effects could not be enabled

is usually a hint that graphics card doesn't support 3d acceleration.

Since the question rather doesn't deliver much info please refer to sys reqirements, installation alternatives and lightweight derivates (Xubuntu, Lubuntu).
https://help.ubuntu.com/community/Installation
https://wiki.ubuntu.com/DerivativeTeam/Derivatives

Requirements for Unity.
https://wiki.ubuntu.com/DemystifyingUnityGraphicsHardwareRequirements