Your graphic card does not have enough power to activate Windows Aero theme, but you wish to have transparent effect on taskbar. No problem, TweakNow PowerPack 2011 has a simple solution for you.

• Open TweakNow PowerPack 2011.
• Go to the Windows Secret tab and click the Start Menu button.
  
  
  
  
• Scroll down to find the Taskbar Transparency Level section.
  
  
  
  
• Set the transparency level you want for Windows taskbar.
• Click the Save button to save the changes.
• If everything works properly, your Windows taskbar should look transparent by now.