siinst.tmp is a Windows process .
If you think that this file contains a virus or another malware, please download a virus scanner.
If siinst.tmp is using too much CPU or too much memory in your system, it is possible that your file has been infected with a virus. Installing an antivirus is recommended.
Not all processes can be uninstalled without the help of a 3rd party tool, especially malware. To see if it can be uninstalled, first go to Start > Control Panel > Add/Remove programs.