I have a Dell XPS T500 desktop computer which I have recently had a
problem with after returning from a trip.  I think while I was gone,
it got struck by lightning and I did not have it hooked up to a surge
protector.  I know, not too bright on my part!  Anyways, the computer
does not boot up anymore.  The computer has power and the light in the
front comes on, but it does not "beep" or access the floppy drive. 
Upon opening the tower/box, I found 2 things.  One, the modem was
fried (it had a big black burn mark across a couple of the
transistors).  The second thing is that there is a small orange light
on the motherboard that is now turned on (I have had the tower/box
opened before and do not remember that light ever being on).  Is this
light an indication of what the problem is?  And if so what is the
problem?

Hi Book Guy ...

Speaking of books ... I found one for you! It's Dell's System Manual
to help troubleshoot your problem.
  - http://docs.us.dell.com/docs/systems/dkub/8868d4.pdf

I say 'help' because there are diagnostics which cover some symptoms
you didn't list in your question.

Nonetheless, I discovered that that orange light on the motherboard is
your system power light, and the fact that it is on is a good thing
... it indicates the motherboard is getting power. See Page 33 of the
book.

Since nothing is happening when you power the computer up, and you
know the modem is fried, you should remove the modem before you run
any diagnostics. Get out your Dell Diagnostics Disk and run hardware
diagnostics. The Diagnostics is on the Dell Resources CD you got with
the computer.

Another indicator which you might want to watch are the diagnostic
lights on the back panel. There should be four of them, and when the
computer is up and running normally are green. Page 161 of the book
explains what the problems are by those lights and whether they are
yellow or green. That's assuming you can boot far enough for the
diagnostic lights to work.

The book also has the beep sequence for problems, but you say your
computer isn't beeping, which won't be of help.

In any case, when you boot your system using the diagnostics disk and
run diagnostics, it should be able to help you troubleshoot what/where
the problem is and how to reset your system. This is provided the
motherboard hasn't been fried, too.

Having had a Dell Dimension, and having fried the motherboard, I can
tell you there was a series of beeps indicating that the motherboard
was dead, so it's hard to say whether or not the lack of any beeps is
a good or bad sign.

The advice for any problem is to see if you can observe where the
problem is, then to use the diagnostics disk and reset the system.

The book will walk you through in terms pretty easy to understand,
including running the diagnostics, resetting the system, etc., and at
least give you a place to start trying to figure things out.

By the way, I fried my motherboard adding RAM ... and Dell replaced it
at no cost because it was still under warranty, and they knew what had
happened, and said it didn't matter - it was covered. I don't know if
this will apply to you, but if push comes to shove, you can ask about
it. I "believe" they said the motherboard was covered for three years
(I honestly can't remember now).

Search terms used on Dell
  - dimension XPS T500 

I hope this helps and that the problem can be easily fixed,
Serenata

Hi ! Bookguy ga. I had exactly the same problem. blew my internal
modem one night when there was a lot of lightning around. So I bought
a new 56k external modem and claimed on my household insurance. Just
got the cheque back. But for comvenience, will in future make sure the
phone line is unplugged from my comp. Am still searching for a unit to
plug into the line to protect the modem.