I was trying to find an image on one of my office PC's a couple of days ago to show one of the guys from MS-Studios, after a few minutes of trawling through folders Pete suggested I install Picasa from Google (does anyone click on the More>> link on Google's home page?).
Picasa is linked towards the bottom right of the "more" page. The application indexes all the images on your hard drive, and provides a simple UI to nagivate and find images on your hard drive.
I really like the application - I found the image I was looking for in seconds (once the drive had been indexed).
The application can be installed from here.