1. Use security software in such a way to avoid conflicts, and perform a complete scan of your computer.
2. Install the recommended anti-malware programs, download all the malware signature updates, and perform a complete scan of your computer.
Remember that for optimum protection of your computer, there is considerably more to do than to simply install and use these programs.
After scanning your computer very completely with 1) Bitdefender (you should search for Bitdefender Antivirus Plus) OR Avira Premium and afterward with 2) SuperAntiSpyware, and 3) Emsisoft Anti-Malware, in that order, (with all the updated malware signatures for each), if your computer still does NOT run well, your computer registry may need to be repaired, or there may be other problems. Follow the specific directions listed here.
You may notice that your resident antivirus program may report that it is incompatible with some of these products that I have mentioned. However, I doubt that you will find any incompatibility since the free versions of these programs are the ON DEMAND versions of the programs, and NOT the versions that run constantly in the background. As long as you scan your computer first with your anti-virus that runs constantly in the background, I doubt that you will have a problem, and your computer will be that much more protected.