The Sims 3 won't install -

[SuperDuperDanDan]

The Sims 3 won't install - get error message "Unable to launch..... The Sims 3_uninst.exe"

[SandArcher]

@SuperDuperDanDan is this a disc or a download? What's your OS? 

Try running Origin as admin: Right-click on the Origin icon on your desktop and choose run as administrator.

Let me know how it goes!