It depends on what "everything" entails, and how far you want (or are able)
to go, and/or how sensitive the information is to you.
If you have confidential data (files, cookies, saved passwords, cached web
pages) on your computer, these all go away if you format the hard drive(s).
Note that this will obliterate EVERYTHING, leaving you with an amnesiac
computer at the end (no Windows, no nothing). If you decide to go this
route, you might want to proceed directly to reinstalling Windows, because
Windows will give you the option to format the hard drives when you install
it.
Depending on how resourceful the people who are trying to get your data are,
you may have to take additional measures to keep them from restoring the
data. It's possible to determine the contents of files even after a hard
drive has been wiped, though it isn't easy. Such countermeasures are
essentially beyond the scope of this newsgroup. HOWEVER, what you're
probably looking for is a disk-wiping tool. Many are available on the web
and what they generally do is write random garbage to your hard drive to
make recovering the original file harder.
Ultimately, it is not possible to keep such data out of a determined
attacker's reach if he has access to your physical hard disk. If your
adversary is sufficiently resourceful, you are probably better off just
preventing him from getting the drive in the first place.
--
This message is provided "AS IS" with no warranties, and confers no rights.
This message originates in the State of Washington (USA), where unsolicited
commercial email is legally actionable (see
http://www.wa.gov/ago/junkemail).
Harvesting of this address for purposes of bulk email (including "spam") is
prohibited unless by my expressed prior request. I retaliate viciously
against spammers and spam sites.
