You are wise to be cautious Franny. I chose that site, because it makes it clear that you are getting the trial version. Here is the Driver Genius main site where I got the trial and Professional versions myself http://www.driver-soft.com/INDEX.html Also, if you are concerned about site security, you might consider this browser add-on http://www.mywot.com/ I'm assuming you have good anti-malware software already?
Franny, if you're not good at finding and installing drivers, try the trial version of http://driver-genius.en.softonic.com/. This should find and down load the latest drivers for you. Just look for the files referring to ATI in the download box, extract and install them.