Linux and Default Ownership

Stats:
Linux System: Slackware
X System: KDE

Priority 1) Is there a way to set all main files to their default ownerships? Because I just ran a test that concluded the following: although root can log into the x system my regular permitted acount cannot. Is there a way to restore default ownerships or someother way to fix this?

Priority 2) Why doesn't my linux system(slackware) execute .exe's(both in and out of x system)? What can I do to allow my system to do this?

Priority 3) Are there any programs for linux that allow the (de)compressing of .zip files?

P.S) When responding please use the priority numbers that way information is easily sorted and seen. Thank you.

:D Main files meaning the ones necessary for use. Like /usr/ and a few others... but I don't know which ones specifically, that's the problem. That's why I asked... is there any way to bring the system back to it's defaults?

edit: because currently, my regular users can't use the system.

I tried reinstalling linux and that didn't work for some reason. So do you know where I can find a list of default permissions? that way I know what to set them to? tia