windows always denies access from installing arduino drivers midway through

plz help me, i cannot install the drivers for the arduino uno. Windows would not recognize the usb so i tried to install the driver manually but windows interrupted me and denied access to installation. I used the same computer and a few weeks before everything was working fine until today when i tried to upload a sketch code to my uno this came up.
avrdude: stk500_getsync(): not in sync: resp=0x00

also the tools/ serial port was grayed out

run as 'administrator' ?