Linda,
CNET usually has a nice review of all of the anti-virus programs, their features and costs - you might want to run a search on their Website.
FYI: In the past, I have had many (too many) different anti-V. and security systems and most of them used too many resources, slowed down my PC, and made working (I telecommute) pretty painful. Currently I have G-Data Antivirus 2011 and have found it to have a nice balance between security and resource usage. Cost was probably ~$50/year.
Good Luck.
Esther
