Hi BJ_GeOrgE,
This program does not slow up your computer whatsoever. It just blocks malicious sites so that your computer cannot make access to them, in rather a similar way like a hosts file. It has other functions where you can make a snap shot of your computer to go back to, etc.
For it to function properly as an additional protection for an IE or Firefox browser, it should be installed on an non-compromised system. So upon installation the comp should be malware free.
The trio Ad-Aware, Spybot S&D, and SpywareBlaster is a classical way of keeping your computer free of spyware, adware, tracking cookies etc. Some install additionally some anti-trojan programs like A-squared, or Ewido-micro (both free).
polonus