There is no cache of any kind. You need to reopen the folder if you modified its content externally (e.g. renamed files from Explorer) while the program was running.
The built-in thumbnail strip is indeed a feature that lights up only on Vista or later. Sticking with XP 64 is clearly a choice that you can make, but you are missing out on more than a half decade of improvements: in our experience Windows 7 is more stable and better performing than any version of XP ever was