Practical advice needed: What do I do now?

[Bob DeMattia]

You could put suppressors on everything, but that may be overkill.  Better
is to first try to find the "leak".
With the AM radio and computer on, disconnect each cable going into the
computer cabinet (except the
power cord of course) and take note of if the noise goes away.  Any cable
that makes a difference will
need an RF choke (a small clip looking thing that goes around the cable).
 For a cable that is leaking RF,
each one of these will tighten up the leak a bit.  You may need more than
one on the same cable.

Here is an easy one to find at Radio Shack, though you can find smaller and
probably cheaper ones
online.
http://www.radioshack.com/product/index.jsp?productId=2103222&CAWELAID=107599340

If you unplugged all the cords and still have noise, you'll need to choke
the power cord.  If that doesn't
work, you'll need to RF proof the cabinet - which could be problematic,
especially if it's plastic.

-Bob