As researched on PDN, I have most prominent cause for this could be due to the anti virus or firewall installed at your workstation. It is blocking the "pg_restore" file, so please try to install after deactivating the anti virus software and turning off the firewall. It worked for developers earlier.
Note : Extract the downloaded Pega personal edition Zip file again and try install from that.
Hope it helps, kindly notify by marking this post as answered for larger Pega audience and tracking purposes.