hi ranjan,
the USB asp fishcl link
http://www.fischl.de/usbasp/
has given a note:
Note: Windows Vista/7 x64 requires drivers with digital signature. Currently there are no official drivers for libusb (USBasp software is based on it) with such a signature. Users reported that there is a tool named “Driver Signature Enforcement Overrider” to avoid the signature check.
have tried that…