Antivirus Software
- Avast Home edition
An excellent antivirus which is free for non commercial usage (Highly Recommended!!)- Antivir Personal Edition
Another good antivirus.
System Softwares/Spyware Removal
- Spybot Search and Destroy
An excellent spyware removal tool- Lavasoft Ad-Aware
Another excellent spyware removal tool. These two tools complement each other.