Should I Buy Anti-Spyware or Antivirus Software

I find in Task Manager that there are over fifty programs are running, and I do not know that the system is slowed down by which program.
Should AdAware or SpyBot be run periodically? And I am confused that which one is better because I find many negative comments about them.
But if these programs are worth money,
I will try.
Any help?
Thanks in advance.
