In these wonderful days of technology, you can basically get anything for free. If you want, no spam, no pop up adds, and no trojans or anything else. First some how download or buy a program called SPYSWEEPER, what it does is scans your computer for spam, and spyware installed on your computer. If you have Imesh or Kazaa, or bearshare etc etc, you will have a lot of pop ups as well. Then get Nortons Internet Security 2003 (it comes with antivirus.) This is very user friendly, and is probably 1 of the greatest firewalls out thier. You can even track the person that just tried to hack you. I mean literally track what city and what state they are in. I would not suggest BlackIce or Lockdown 2003 if you are not familiar with computers. Oh and maybe microsoft baseline security. Nortons has a intergrated spam and pop up add filter, personally i think it is much better then the Adware, or addsubtract, or anything on the market.
And the wonderful thing of it all is if your not afraid too, you can download all of this off of like a Bearshare or any peer2peer search engine. If you where to buy:
NIS2003 $150
Spysweeper $30
Blackice $200
Lockdown 2003 $150
Microsoft baseline Security: Free