I am not able to change visual effects ?

If you cannot enable Desktop Effects it means that either your graphics card does not support them, or the driver lacks 3D acceleration.

Please post the output of these commands so we can help you:

lspci
cat /etc/X11/xorg.conf

hi,

I am pasted the output of lspci

lspci
00:00.0 RAM memory: nVidia Corporation MCP61 Memory Controller (rev a1)
00:01.0 ISA bridge: nVidia Corporation MCP61 LPC Bridge (rev a2)
00:01.1 SMBus: nVidia Corporation MCP61 SMBus (rev a2)
00:01.2 RAM memory: nVidia Corporation MCP61 Memory Controller (rev a2)
00:02.0 USB Controller: nVidia Corporation MCP61 USB Controller (rev a2)
00:02.1 USB Controller: nVidia Corporation MCP61 USB Controller (rev a2)
00:04.0 PCI bridge: nVidia Corporation MCP61 PCI bridge (rev a1)
00:05.0 Audio device: nVidia Corporation MCP61 High Definition Audio (rev a2)
00:06.0 IDE interface: nVidia Corporation MCP61 IDE (rev a2)
00:07.0 Bridge: nVidia Corporation MCP61 Ethernet (rev a2)
00:08.0 IDE interface: nVidia Corporation MCP61 SATA Controller (rev a2)
00:09.0 PCI bridge: nVidia Corporation MCP61 PCI Express bridge (rev a2)
00:0b.0 PCI bridge: nVidia Corporation MCP61 PCI Express bridge (rev a2)
00:0c.0 PCI bridge: nVidia Corporation MCP61 PCI Express bridge (rev a2)
00:18.0 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] HyperTransport Technology Configuration
00:18.1 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] Address Map
00:18.2 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] DRAM Controller
00:18.3 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] Miscellaneous Control
02:00.0 VGA compatible controller: nVidia Corporation GeForce 8500 GT (rev a1)

Output of cat /etc/X11/xorg.conf

 cat /etc/X11/xorg.conf
# xorg.conf (X.Org X Window System server configuration file)
#
# This file was generated by dexconf, the Debian X Configuration tool, using
# values from the debconf database.
#
# Edit this file with caution, and see the xorg.conf manual page.
# (Type "man xorg.conf" at the shell prompt.)
#
# This file is automatically updated on xserver-xorg package upgrades *only*
# if it has not been modified since the last upgrade of the xserver-xorg
# package.
#
# Note that some configuration settings that could be done previously
# in this file, now are automatically configured by the server and settings
# here are ignored.
#
# If you have edited this file but would like it to be automatically updated
# again, run the following command:
# sudo dpkg-reconfigure -phigh xserver-xorg

Section "Device"
 Identifier "Configured Video Device"
EndSection

Section "Monitor"
 Identifier "Configured Monitor"
EndSection

Section "Screen"
 Identifier "Default Screen"
 Monitor "Configured Monitor"
 Device "Configured Video Device"
EndSection

Hi,

I got the solution.
I did not actiavted it.

I'm glad you solved your problem.

What did you activate? The nvidia video driver?