Laptop: Inspiron 600m

I have Ad-aware SE Personal

I have SpyBot Search & Destroy

...are the above strictly "spyware" protection?  Do they feed off of each other when I run them separately (one catches what the other doesn't)?

I am going to purchase McAfee Anti-Virus software (do you agree that this is a wiser investment) as opposed to downloading free software from download.com? Or if not, what is the common anti-virus on download.com?

 

Anti-virus and spyware are separate functions right?

 

Thanks for your time..... MaryJane