I once tried out the demo of this program. It is a program which scans your drives for images and can help you find them (without tagging) by color, time, or content. It was a time-limited demo and I decided it was not powerful enough yet for me to invest the $20 in it. Well, I checked on their website today, and they have made it free! So give it a try. It is certainly in the development stage, and it runs a bit slow, at least on my laptop, but it is cool.
Can't find the photo of Uncle Ted wearing that orange polka dot tuxedo taken a few years ago at the 4th of July party on the beach? No problem. Your nine trillion gigabyte hard drive is no match for Photology! You know the expression, "finding a needle in a haystack," right? Thanks to Photology, haystacks of photos will get a lot smaller, making it much easier to find the "needle" you're looking for – even if that needle is an orange polka dot tuxedo.