Hello RAKESH KHATRI,
Thank you for writing. Most cases having similar symptoms
are fixed by a display driver update. Please, make sure that you are using the latest one for your Vista machines. In addition, you can experience weird styles behavior if you are using a terminal service e.g. Remote Desktop. We are working on this issue, although unfortunately it has not been resolved yet. Do not hesitate to contact me again if you have other questions.
the Telerik team