Have you tried leaving it for a bit... it may be trying to load a rather large picture for preview, which will cause the window to apparently freeze.
In 98, you could set a folder that opens to not display as a web page, and then go to the folder options and set all folders to be the same. That should stop if trying to preview.
There's a way to disable the preview used for AVI files in XP, but I'm not familiar with XP so I don't know how to do it. Some other forum members should be able to help there though. I've seen a few posts about it, if I find the method I'll post it.