I am having problems with my Dell 1390 wireless card (under Vista).
When I go from one network to another, it can't find the other one or
it connects with limited access (local only).

That's problem #1 -- very irritating, but I haven't Googled it yet.

What is more worrisome is that when I went into my Programs and
Features applet (formerly Add / Remove Programs under XP), it appeared
that somehow things got corrupted.  Instead of program names for most
things, there were things like #7400 as an entry.

I did a System Restore which fixed the problem.

A few days ago I installed Zone Alarm Free for Vista, and I restored
prior to that point.  Otherwise I don't know what could have corrupted
things.

As far as the wireless Dell 1390, I wish I had chosen the Intel
version.  I have had many intermittent problems.

I am close to going back to XP to see if things are more stable there.
I have had a chance to try Vista, and although I like some of the
features of the new explorer, other than that I might as well be
running XP anyway.  I won't be missing anything other than some of the
power management features that I can tweak under Vista.

MS says SP1 for Vista isn't going to come out until 2008.