Do I need Ad-Aware if I use AVG9?

I use both. It’s better to be safe than sorry.

No. Both programs provide you with security against viruses and spyware, so there is no need to have both installed, and moreover they might even conflict with each other. You should choose to have just one such program, and if you haven’t considered other options, consider trying Microsoft Security Essentials, Avira AntiVir Personal, Avast Home Edition, or IObit Security 360.
For more security, in addition to anti-malware software, you can install Comodo Firewall and use it instead of Windows Firewall.

Yes… also use Spybot Search & Destroy and CCleaner.

I would also say no. I simply run the blocklists on spybot and Spyware Blaster. Combine those with Adblock/noscript on Firefox and I’ve never even seen a virus or spyware make it through to my antivirus.

What doggywuv says is true though. Having multiple programs that do the same thing can cause damaging conflicts. I’ve completely disabled a system by installing two AV programs. (I also run Avast =) )

Couldn’t hoit™.

You want protection from two different things, viruses and malware/spyware

Ad-Aware Free is not an anti-virus product.

Ad-Aware ($26.95) Plus does both
AVG Free 9.0 does both.
Microsoft Security Essentials does both.

Sorry, @jaytkay is right, actually Ad-Aware Free doesn’t provide protection against viruses, so it is not a substitute for AVG Free. But I the two still may be incompatible and cause problems together.

Ad-Aware (the non-live version) does not usually conflict with antivirus software such as AVG, and in fact, it can catch spyware that AVG misses.

But since your AVG has an Ad-Aware type program built into it, i suggest downloading ThreatFire, which uses a totally different method of catching viruses and malware, by monitoring your system’s vital signs, instead of relying on virus definitions. It’s a good adjunct to whatever protections people already use, and its low on resources.