Spyware and virus alerts

I have Symantics Anti-Virus installed and I run updated Ad-Aware and
SPYBOT.

All of a sudden,I'm getting a lot of pop-ups saying that my system has
Spyware, malware, viruses (i.e., Trojan-variants, Worm, etc) and I'm
getting getting prompts to download various "security software" (for
example: Virus Ranger, AntiSpy Kit, WinSecure Antivirus, WinSpy
Control, WinAnonymous, etc).

How can I get clean my system and stop the pop-ups and prompts?
.