Well, it is a personal preference but I feel that McAfee is better than Norton but truth be told, all mainstream virus protection programs have problems because hackers write the viruses to get around them. As for your clean up issue try:
Spy Bot Search and Destroy
www.safer-networking.org/
Spyware Blaster
http://www.javacoolsoftware.com/spywareblaster.html
Spyware Doctor
http://www.pctools.com/spyware-doctor/
Ad-Aware SE Personal Edition
http://www.download.com/3000-2144-10045910.html
Those revome, as the names suggest, spyware and adaware but unless your computer is crashing, I'm geussing Norton has prevented viruses and that it is spyware or adaware. If it is a virus, then this stinger by McAfee has done well for me in the past:
Stinger
http://vil.nai.com/vil/stinger/
Those should all be free. Hope that helps.