Vst instruments in Nuendo 4.3.0

I am not able to open vst instruments in my nuendo. The list of VST instruments are not shown, but before i could get the list from the vst instruments. Now its only showing two inbuilt vst such as SYNTH and VSC. Can any one help me in this matter. The vst software’s are installed in the system and i could also open it through FL studios. Should i reinstall my windows. Please help me.

Waiting for a favorable reply…

Thank you