Don't be a victim to malware. Update to the latest service pack to stay up to date with security updates and reduce the chances for infection.
Windows Service Pack Lifecycle
As shown in the table below from the Windows lifecycle fact sheet - Microsoft Windows, the only services packs still supported are for Windows XP SP3, Windows Vista, SP2 and Windows 7 SP1.
Desktop operating systems Date of availability Support retired Windows XP SP1 August 30, 2002 October 10, 2006 Windows XP SP2 September 17, 2004 July 13, 2010 Windows XP SP3 April 21, 2008 Windows Vista SP1 February 4, 2008 July 12, 2011 Windows Vista SP2 May 26, 2009 Windows 7 SP1 February 22, 2011
Update to Windows Vista SP2If you are not sure if you have installed the latest service pack, you can easily find out by clicking the Start button, right-click Computer and select Properties. SP2 will be listed in the Windows edition section if it has already been installed.
In the event you discovered SP2 has not been installed yet, Microsoft has provided very complete instructions installing Windows Vista SP2, including recommendations to follow prior to updating to SP2. Following the "Before You Begin" recommendations at Learn how to install Windows Vista Service Pack 2 (SP2) will help ensure a smooth upgrade to SP2.