Here are some links I have found helpful.
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1   Link   House Call Antivirus
Trend Microâ„¢ HouseCall is an application for checking whether your computer has been infected by viruses, spyware, or other malware. HouseCall performs additional security checks to identify and fix vulnerabilities to prevent reinfection.
2   Link   Microsoft Update
Keeping your operating system up to date is an important step in maintaining your computer. Microsoft regularly releases updates to its products which can be found here.
3   Link   CCleaner
CCleaner is a freeware system optimization, privacy and cleaning tool. It removes unused files from your system - allowing Windows to run faster and freeing up valuable hard disk space. It also cleans traces of your online activities such as your Internet history. Additionally it contains a fully featured registry cleaner.