Well, if you want to change some thing remotely on any computer you will mostly need an administrator password, but you can also do that with another account, depending on the policy of that account. Yes you can recover a password remotely if you use another computer on the same network. Get cain & abel from Http://www.oxid.it
. the new version is v4.9.9, or you can use ophcrack from http://www.ophcrack.org
and then use cryptanalysis with ophcrack tables or rainbow tables, I prefer ophcrack tables because they are more compact then those of rainbowtables and very very very effective. Some tables can crack 14 charachter passwords in seconds consisting of this charachter set: abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWX YZ1234567890!@#$%^&*()~_+=- now, that comes with 99% success probability. You can also use that same method with cain and abel.