I wanted to reinstall Alt1 due too some issues, but when i open the Setup.exe, the instalation wizard just stays at "Installing Alt1 This shouldn't take too long". I tried deleting everything Alt1 relted on my pc, but still no luck.
Your antivirus might be preventing the installer from running, please make sure it isn't blocking RuneApps.Alt1.exe.
You can always use one of the standalone releases if it still doesn't work. There is more information here.