Need To Run Software As A Background App (Service?)

I have a Zip archive which was encrypted with a password 7 months ago that
has now been forgotten.

Naturally I would like to get access to a distributed network that could
brute force the password probably within a day or so, but that's not going
to happen.

The brute-forcing software I am using includes something called "Zip
Password Recovery" (now unfortunately averaging only 800,000 passwords per
second on a 1.8 GHz P4 CPU with 640 MB RAM) running XP Pro.

I also have something called "Ultimate Zip Cracker" (trial version) which
was doing 18 million pswds/sec, the machine being an 2.6 GHz Athlon X2
dual core 5000+ with 3 GB RAM running Vista HP. I like the UZC software
because it allows me to trim the character set to characters I think are
used (56 total) whereas the others force subsets that I might not try
otherwise.

In my initial attempts I have already determined that the password is
probably 8 chars or more long. Dictionary attacks are no good, since the
password likely involves a foreign word I used, and there is no dictionary
I can find for the foreign language used. I think the password is a
<foreign word--possibly slang> + <calendar year, like '2007' or maybe a
birth year>.

Anyway, these computers are used by others. The apps run within a logged-
on user, so whenever the user logs out, the app gets shut down. The UZC
is supposed to save its state every 5 min so that I can return to it...for
some reason it's not doing it.

But I still want to run any software in the background so that users are
not aware of it and don't shut it down.

I have remote access to these systems: Remote Desktop for XP Pro, and
TightVNC on Vista HP (which does not seem to be behaving).

How do I put these apps in the background, or run as services?