When I connect to the internet (dial-up connection, Win XP) I get a
message saying something like "Your computer is shutting down in 60
seconds", which is exactly what happens. I was told by a friend this
is a virus/worm called the "welch worm"(?). Where can I find a fix for
this? How can I prevent this type of thing from affecting my pc in the
future? (I don't believe I opened any infected attachments lately).

Good Day bigsticks-ga,

Before I go into depth on an answer, here is a way you can abort the
shutdown after you receive a 60 seconds warning:

1. Click on the start button, and select run.
2. Type in “shutdown –a” and click OK (no quotes).

This will abort the shutdown. If you are using the infected computer
to read this answer, hopefully this command will prove helpful in
reading the full answer, and implementing the fix for the problem.

The virus you are referring to is most likely the Blaster Worm. It has
a few names though. You are one of many people that got hit with it,
and as you suspected this virus is not a result of a file attachment
but a direct access to your computer via port 135 (note that this is
the original port used by the virus, since then it has begun to spread
via other ports too). What ever the virus is, the below instructions
will help you get rid of it.

Here is how to remove the virus and help prevent this and other
infections in the future:

1. Get the free AVG virus checker:

WEBSITE: Grisoft's AVG Anti Virus
URL: http://www.grisoft.com/us/us_dwnl_free.php

2. Install and run it. Keep it always running to prevent future
problems.
By default the AVG software will update itself every two weeks to keep
the virus database up to date.

Now that you have removed the virus and have the AntiVirus software
running, we want to further ensure that this does not happen again. We
are going to do that with the help of a software firewall.

WEBSITE: ZoneAlarm
URL: http://www.zonealarm.com

Instructions: The free version of the firewall might be hard to find.
Follow these directions to access it:

Click on the "Home/Office Products" link on the ZoneAlarm website.
Click on "ZoneAlarm" which will become visible under the "Home/Office
Products" link after clicking it.
Under the "graph" with features you will see a red "Download" Icon.
Click it.
At the top of the new page that loads, click "Download FREE ZoneAlarm"

Install ZoneAlarm, and always keep it running.  It will block all
unused ports on your computer. Please read the ZoneAlarm first use
tutorial that will load during the installation. It will give you some
quick tips on what to expect from the firewall, and how to use it.

This is all that you need. I hope that you are now virus free, and
protected against any other viruses.

The source of the information is my prior experience with this and
other viruses.  There was no online search strategy used to deliver
this information.

If any part of this answer is unclear, or if you cannot complete any
of the above steps, please ask for a clarification with more
information on which part of my answer you are having trouble with.

Thank you for your question.

Regards,
slawek-ga


Regards,
slawek-ga

Haven't tried it yet, but sounds convincing!