Missing (but not really) Icons in XP

My wife’s Computer (XP Pro constantly updated automatically) has a bug which seems to periodically delete certain Windows Apps like Outlook Express or IE, Calculator and some others I can’t remember now.

Anyway I copied the exe files from my own XP machine to replace them in the directory they are missing from and I get the message to say the file is already there do i want to overwrite……hmmm…..look again….no its not so i say yes overwrite. All works fine after that…

Just wondering if there is a known bug that does this or is it a known XP Problem that I have missed learning about???

Just not too sure about continuing to online bank using this machine…..help someone, please….
Thanks
Wayne