Can free anti-virus and anti-spyware software adequately protect a computer, compared to commercial

My anti-virus and anti-spyware provider - Computer Associates - recently upped their prices, and I'm wondering - can I adequately protect my computer using freely available software like Ad-Aware and Spybot, or do I really need commercial protection software?

If I can adequately protect myself with free software, what all should I get?

Can free anti-virus and anti-spyware software adequately protect a computer, compared to commercial software?windows

Yes and no.

Even if you buy anti-virus and anti-spyware programs you aren't completely safe on the internet (not even if you also buy a firewall).

Malware can and does get on to computers via programs such as Flash player, Adobe Reader, Apple QuickTime, Java, etc. A good anti-virus / anti-spyware program should find and remove it when it's on but it can't be relied upon to keep ALL malware off your pc.

You can get pretty much the same level of security from free programs, *if you choose well*.

Yes, there are plenty of scam and malicious anti-spyware programs out there but there are also some very good freebies.

In some cases, e.g. AVG, etc, they are a (good) way of getting people to try their product in a market that is dominated by Norton %26 McAfee. And yes, in some cases altruism is the motivator. Might be hard to believe in a cynical world but, nevertheless, it's true. E.g. the MVPS Hosts file and SpywareBlaster.