Ok.. anti virus.. DO NOT TOUCH AVG WITH A BARGEPOLE.. it really is a pile of cack, one of the worst detection rates of any antivirus.. absolutely spiffingly awful...
Anti Virus/Firewall We have used for the last three years comodo internet security, FREE, as it has the advantage of a having both AV and FW built in one and a very low memory footprint.. most of the time around 15,000k
http://www.comodo.com, free lifetime licence..
review
http://fileforum.betanews.com/detail/Comodo-Internet-Security-32bit/1224699488/1
The only other AV i particularly recommened is Avast, but then you do need to find a suitable free firewall, Kerio used to be great but is a bit of a memory hog now...
Spyware As previously mentioned, spybot search and destroy, install, update, immunize and then scan regularly....
http://www.safer-networking.org/index2.html
General cleaning.. CClean - again free, probably the best general cache cleaner out there, the registry cleaner is also very effective and safe just backup the registry as promted before cleaning..
http://www.ccleaner.com/download
Defrag - the fastest, most effective and user freindly defragger ive found in years is Auslogics, again FREE..
http://www.auslogics.com/disk-defrag
so i agree on spybot, and ccleaner, but strong hate avg and zone alarm (zone alarm since v7 has even more issues than avg)
also stands to reason, dont use internet exporer, for higher security use firefox, for even better security use opera.. but dont use IE
also,
check the make and model of the new one, if it came with vista, you may be able to upgrade to windows 7 for free.. check this link and follow through the prompts under manufacturer..
http://www.microsoft.com/uk/windows/buy/offers/upgrade.aspx