Hi jyaekim,
First thing is your c drive\users restricted for 3rd party installation.
One solution I suggest here
go to temp folder for eg- c:\Users\user_name\AppData\Local\Temp\Rtmpo1234\downloaded_packages
remove packages from it.
Remove R and Rstudio
Reinstall it but whenever you install both software then change path to C:\Documents
this will resolve your issue
try this and let me know....!
Regards
mahesh