Regedit is not saving the change and I have to make the same change every time I restart

Dear Experts,
Every time I start my windows XP I have to run regedit and change Cache value under
HKEY_CURRENT_USER \Software \Microsoft\Windows\Current version\Explorer\User Shell Folders
On the right side of the pane under cache it shows :
F:\Temporary Internet Files
I change it to
%USERPROFILE%\Temporary Internet Files
And system works fine if I don’t change it gives me problem with word and outlook.
This problem started coming up few days back though I am not too sure but I think system update was running and I removed a USB after system said its safe to remove.
Can you please tell me how to permanently save the above change in regedit
Please advise.
Best Regards/VKS