how to completly delete unneeded files

I am wondering how one would go about deleting all files that are no longer
need.

And also what is Application data for? How can you clear all files that are
potentially dangerous or are just taking up space?

In news:23EA9B15-B2B2-4523-83F1-85C1C1D08F38@microsoft.com,
Mark Twain <Mark Twain@discussions.microsoft.com> typed:
> I am wondering how one would go about deleting all files that are no
> longer need.

Data files you or another user created, such as My Documents? Just select
and delete them.

>
> And also what is Application data for? How can you clear all files
> that are potentially dangerous or are just taking up space?

Use Add / Remove Programs. Don't just delete files if you want your PC to
work properly....you might render it unbootable.