As others have correctly stated, Winrar does not and cannot install anything into the game, and for Sims2Pack files, just right-click on them and choose Clean Installer to handle and install them.
That said, if you don't like Winrar (in my own opinion it is bloated, crappy nagware), then uninstall it and use something else to unpack zip and rar files. Personally, I like the free, safe, unobtrusive and user-friendly 7-zip:
http://www.7-zip.org