Microsoft Security Essentials, Best Antivirus program.

I am often asked; “What security software do I use for my main layer of protection?
My answer is, “Microsoft Security Essentials".

Microsoft Security Essentials provides real-time protection for your home or small business PC that guards against viruses, spyware, and other malicious software.

Use Microsoft Security Essentials to guard against viruses, spyware, and other evil software. It provides real-time protection for your home or small business PCs. Microsoft Security Essentials is free designed to be simple to install and easy to use. It runs quietly and efficiently in the background so you don't have to worry about interruptions or making updates.

Before installing Microsoft Security Essentials, we recommend that you uninstall other antivirus software already running on your PC. Running more than one antivirus program at the same time can potentially cause conflicts that affect PC performance.

A performance table for MSE by cNet team:

Security program	Boot time	Shutdown time	Scan time	MS Office performance	iTunes decoding	Media multitasking	Cinebench
Unprotected system	42.5	11.28	n/a	917	180	780	4,795
Microsoft Security Essentials 2	54	18	1,560	1,038	201	800	4,790

Features and Support:

• MSE uses both definition-file and real-time protection against viruses and spyware, and also provides rootkit protection.
• Along with the quick scan and the full scan, there's a Custom scan option that lets users select specific folders or drives to scan according to their need.
• You can set USB keys and other external devices to automatically get scanned.
• The program installs a context-menu option for on-the-fly scanning in Windows Explorer, too.
• Microsoft Security Essentials automatically checks for and downloads virus definition updates which are published three times a day to Microsoft Update, or a user can manually download updates also.
• File downloads and e-mail attachments are also scanned.
• System Restore points are created before removing found malware/viruses.
• Microsoft Security Essentials requires no registration or personal information.