After buying a Win Vista laptop, I also purchased PhotoImpact X3. Corel Media One was included as an accessory that need not necessarily be installed. But I installed Corel Media One anyway, and subsequently became familiar with the somewhat hidden location of the app's sidecar thumbnail files. It turned out that if the user wanted metadata appendages or small thumbnail views in PhotoImpact's native file format, that Corel Media One was required.
Eventually I was able to successfully uninstall Corel Media One, and found that doing so did not impact my occasional use of PhotoImpact X3. I wonder what happened after that? I had never used PSP until I bought PSP X4 for a new Win7 laptop.
Do the later versions of PSP perhaps quietly include many of the features of Corel Media One? And thus the necessary sidecar thumbnails for certain file formats? Is it possible to deselect this feature and also avoid Corel's metadata tagging in PSP conveniently? Dunno. I only use jpgs and Irfanview, and occasionally wish that I had PhotoImpact on my current computer because it took me years to scratch the surface on it. At this time I still buy promising applications, just like the old dos days. And just like the old dos days, I seldom use them because I would rather watch someone else's work product on TV.