Not necessarily.
While you can encrypt data on a couple of versions of Vista, I'd have to
say that it would not offer much if any protection in this situation.
I say this because EFS encryption is tied to the account, and if you're
actually in the account - as you would have to be to service the system -
the data is not encrypted to you. It can be simply copied away, and at
worst, the account certificates can be exported and the data copied off
wholesale and decrypted on another machine.
And of course EFS isn't available on any version of Vista or XP with Home
in the name.
EFS encryption is really only of value in cases such as theft or
unauthorised system access. As soon as you give someone access to your
account, EFS protection is just gone.
You could use a 3rd party encryption tool that uses a separate password.
Then only those who need that specific data have access to it, not anyone
who walks up or is given access to the system. The system can be
serviced without giving out that password. This has the added advantage
of not being subject to account damage from Windows reinstalls.
That said, granting access to a system for service or use does *not* grant
ownership of or rights to its contents, and privacy laws probably also
apply (depending on jurisdiction).
Legal action should be initiated as quickly as possible, and whether
lawyer or law enforcement is first should be decided by simple
availability. If the best that can be done right now is to drop by a
police station and file a formal complaint on the record, that's probably
the best idea.
Neglecting to take action can be regarded as approval, and result in a
loss of rights.
HTH
-pk