Ok, this might not be an issue for all systems, but few (like mine :cubs:)
Here is the problem. I will explain with screenshots
First, the good one which is from Vista Control Panel,
And the bad one which is built using Visual Studio 2005/2008 beta 2 and also with Expression Blend,the result is same
Can you notice the tick mark above, how bad it looks :bored:
To solve the above problem, we have to set the rendering option for CheckBox as below,
RenderOptions.EdgeMode="Aliased"
So, if anybody are stuck with this problem, do not forget to set the RenderOptions for your CheckBox !