Can't install programs by left clicking

Hi, I've been browsing this forum for hours now and still don't know what's wrong with my laptop.

Some background: My wife and I have a Lenovo Z585 laptop with Windows 7 Ultimate. Recently she accidentally installed some adware/malware name SweetIM. That caused a lot of errors in our browsers. I was able to remove all of it through spybot & avast, but one problem still remains.

Problem: Every time I try to install a program by left clicking, it wouldn't install. If I right click with "Run as administrator", it would work. While this is a short term fix, but I would to know why I can't left click/install like usual. For example, if I try to install spybot, I get the following message:

"Unable to execute in the temporary directory. Setup aborted.
Error 5: Access is denied."

When I try to install common programs like Adobe Flash or Firefox, nothing would happen with a left click.

When I enabled the built-in elevated administrator account, left click to install is no problem in the Administrator account. However, it still doesn't work in the User account. We only have one user account between the two of us, and everything I've checked showed that it is admin.

I've already ran Avast virusscan/hijackthis/spybot and can't find any issues. Any help is appreciated.