When I hit File/Open in PS, the dialog box always opens in"details" and I have to hit the select view icon and chose "thumbnails". I've looked in preferences but can't find anything to change the default to Thumbnails. Is it that you have to do this somewhere in Windows OS ?
What versions of Photoshop and Windows are you running?
I ask, because running Photoshop CS5 and Windows 7 x64 when I select a view - e.g., Large Icons (which yields thumbnails) it sticks. Make sure you actually open a file after making the change.
You probably won't be able to change the default dialog view in XP. That's a feature upgraded in the newer versions of Windows.
People sometimes ask me what's better about Windows 7 than XP. This is one small thing.
I did read about an undocumented "trick" for XP once, but I've never seen it actually work myself and I chalked it up to lore... But hey, trying it would be easier than upgrading to a newer version of Windows, right?
Change the view to the one you like (e.g., thumbnails), then hold down the Control key and close the dialog with the X in the upper-right.
Hope it works (but I'm not holding my breath).