Thanks Ursula, but that is more info than I knew existed.

I was under the impression that sit files were mac, and zip were for PC's.

I've been downloading exe files without knowing anything.
Maybe that's the reason my computer is acting weird now.

I've had to reboot, and it still isn't acting right. I just wanted to download a safe file that had a zip ext. on it, that would be okay and safe.

So if I own a PC, then just stick to zip? files?

thanks for your info and I did go to those links you added for the files ext. info.