deleting .zip files

Your first question: yes, it is safe to delete such zip files, if you are certain that you will never need them (e.g., if the installed program should become corrupted.  I have created a special folder (called Archives) where I keep all such files, in case I ever need them again.

As to the second questions, programs that are being installed often create a set of temporary files during the installation process which are deleted after installation is complete.  They do not usually go to the recycle bin,  But, it is in all probability safe to empty the recycle bin (with the file in it) since the file cannot be used by the program while in the recycle bin anyway.

Thanks for your replies. I can now make a better educated decision on these files.

Generally, if I download a program, update, etc, I keep the zip file or whatever download file there is, in case it needs to be reinstalled again.  Periodically, I back up my "download" folder to a CD-R and "clean out" my Download folder, but that's all.  However, if you want to delete the zip file it's not a problem, you can always download it again if you have a problem with that particular program/file (if it's still available).

Again, generally, I don't delete files from the recycle bin.  I let Windows manage that, and a couple of times I needed to restore a file that was deleted (either by a program or by me) because of a problem.  If I had kept the recycle bin empty I would have been "Sorry Out of Luck".   I'm not sure if System Restore uses files from the recycle bin or not (I tend to lean towards it doesn't) but that is another issue, if you ever have to use System Restore.