problems with exploring Win2000...

everything was working as it should...I had Photoshop and PhotoImpact as my image editing programs, and when I browse a folder and highlight an image file, the preview would show at the left hand side.... I installed MGI Photosuite III SE and some Digi-viewer program and now the preview that showed before no longer comes up..not even in thumbnail view.

I tried uninstalling the two programs and even re-installing photoshop but nothing's working ...the only image file that seems to still be "previewable" is jpeg.... this doesn't seem like such a big deal but I've got thousands of images on my computer and I create web pages for friends and this set back takes a toll on the way I manage my files and browse my comp...

Does anyone have an answer for this problem? Your help would be much appreciated!