f> How to set registr or PC to allow del index.dat or other files
f> which are protected?

That depends from how they are protected. There are several different
reasons why one may not be able to delete a file. (I can think of at
least six.) But since you haven't told us what you are doing or the
error messages that you are seeing, there's no way that anyone can
tell which of those reasons may be applying.