Other free net security stuff:

Only run ONE antivirus program on your computer.

All of these are free and recomended in the litriture, but there are "clones" with similar names that charge or may even be malware so look carefully before you download any utilities from the net.

It's a good idea with XP (standard with Vista I believe) to download and install Microsofts Windows Defender, free and good at sorting hijacks etc.

AVG from (free.grisoft.com) these people also do an anti-malware for free and a rootkit scanner again for free. Vista/XP/2K compatable.

Zonealarm do a free firewall, but last time I checked it had isues with Vista. Fine for 2K and XP and may well be sorted for Vista too by now.

As stated in other posts Avast is free, need registering every year (free) and is the full version tat the sell to comercila ustomers.

AVG is slightly cut down in the bells and whistles, but is fully functional in scans etc.

Free and also worth looking at are Spybot Search and Destroy (safer-networking.org) but be carefull of imposters, and Adaware (lavasoft.com) again free.

Last but not least HijackThis (spywareinfo.com) defacto tool for generating system reports for use in help forums.

Hope this helps.