Avast is excellent and free. Make sure to register and get the free one year subscription. Their website will guide you through setup and installation and what not.
Web Shield is a unique feature of avast! that enables it to monitor and filter all HTTP traffic coming from Web sites on the Internet. Since an increasing number of viruses (and other malware, such as adware, spyware and dialers) are being distributed via the World Wide Web, the need for effective countermeasures has also increased. Web Shield acts as a transparent HTTP proxy and is compatible with all major web browsers, including Microsoft Internet Explorer, FireFox, Mozilla and Opera.
Unlike most competitive solutions, Web Shield's impact on browsing speed is almost negligible. This is because of a unique feature called "Intelligent Stream Scan" that lets the Web Shield module scan objects on-the-fly, without the need of caching. Stream scanning is performed in operating memory only (without the necessity to flush the contents to disk), providing maximum possible throughput.
I use avast for AV. Antivir is suposed to be really good, and a lot of people will recommend AVG Free.
As for spyware, i rely heavily on spywareterminator right now, mainly due to its real time protection. It also detects changes to the registry and lets you allow or block them. I also run superantispyware, spybot search and destroy, and AVG antispyware free edition.
Dont think you can go wrong with any combo of the above.
Spyware Terminator, AVG Anti-Spyware, Ad-aware. They are the three I use and they do a fatanstic job. Of course, other people will post what they use or what they recommend, so you'll have heaps. As long as you use a good 3-4 of those programs in tandem, you'll rarely have an issue. Just make sure you only use one any-virus program, as they will conflict otherwise, but spyware programs if doesn't matter how many you use.
Spyware Terminator takes like 3x longer then all the other programs to scan. The other two alone are not good enough. I have both and they miss an enormous amount of threats. After scaning with them I scan with others and find 100+ threats.
As I'm sure many other people will agree with me, it isn't 100% true.
It only is true for anti-virus, but not with anti-spyware programs. You can use as many anti-spyware programs as you like and it won't stuff anything up.
AVG and Avast are by far the best and they are free, so cant beat that,,,,,,,,o ya they also dont hog your system resources like the other virus scanners such as Mcafee