I just purchased at Dell Inspirion E1505.  I opted not to buy the
virus software offered to me at the time of purchase as a friend
advised that I could download software just as good for free.  Is this
true?  If so, what's the best free anti-virus software and if not,
what anti-virus software should I purchase?

Hello jmarmonster-ga,

Thank-you for your question.

Your friend is correct that you can download anti-virus software for
free from the internet.  Some of the packages are just as good and
some are even better than some of the commercial packages you can buy.

I believe the free anti-virus packages you have to choose from are:

1) Grisoft AVG Free Edition 7.1
"AVG Free for Windows is a free anti-virus protection tool developed
by Grisoft for home use. We invite you to join the millions of
satisfied customers worldwide who have downloaded the software and now
enjoy the benefits of AVG Free for Windows."
http://free.grisoft.com/doc/2/lng/us/tpl/v5

2) avast! 4 Home Edition
"avast! 4 Home Edition is a full-featured antivirus package designed
exclusively for home users and non-commercial use. Both of these
conditions should be met! Our company offers the Home Edition free of
charge, since, in our
opinion, it is possible to avoid global virus spreading by efficient
prevention; however, many user are not able to or do not want to pay
for antivirus software."
http://www.avast.com/eng/avast_4_home.html

3) AntiVir PersonalEdition
"You will recognize the free of charge AntiVir PersonalEdition Classic
with its characteristic red umbrella. The Premium variant is
additionally accompanied by a silver umbrella that symbolizes
additional protection through an extended functionality of the Premium
Version on the one hand and on the other the cooperation with the
Auerbach foundation."
http://www.free-av.com/

4) ClamWin
"ClamWin is a Free Antivirus for Microsoft Windows 98/Me/2000/XP and 2003.
ClamWin Free Antivirus comes with an easy installer and open source
code. You may download and use it absolutely free of charge."
http://www.clamwin.com/content/view/71/1/

5) BitDefender 8 Free Edition
"BitDefender 8 Free Edition is your chance to use one of the world's
most effective antivirus engines for free!"
http://www.bitdefender.com/PRODUCT-14-en--BitDefender-8-Free-Edition.html

The following website may help you decide which best fits your needs:
http://www.firewallguide.com/anti-virus.htm

The article contains links to a number of reviews of the latest
versions of the various manufacturers software packages which should
help you decide which one meets your needs.

It is practically impossible to say which package is "best" as if you
read through some of the reviews on each package you will see.  I
would recommend trying a few different packages out and seeing which
one you find easiest to use (an easy to use piece of software is one
you will use regularly and this is exactly what you need with
anti-virus software as you will need to run it and update it at least
weekly!).  Personally I used to use AVG and found it suited my needs
perfectly for my laptop.

If you require any further assistance please do not hesitate to ask
for clarification.

Further Reading:
http://www.av-test.org/index.php3?lang=en
http://en.wikipedia.org/wiki/Anti-virus
http://en.wikipedia.org/wiki/Anti-virus_software
http://www.av-comparatives.org/
http://www.icsalabs.com/icsa/main.php