To further clarify, per Microsoft.com website:
Support for Windows Vista without any service packs will end on April 13, 2010.
Support for Windows XP with Service Pack 2 (SP2) will end on July 13, 2010.
Note: There's no SP3 for the 64-bit version of Windows XP. If you’re running the 64-bit version of Windows XP with SP2, you have the latest service pack and will continue to be eligible for support and receive updates until April 8, 2014.
So, if you do not want to upgrade to Windows 7, get SP2 for Windows Vista or SP3 for Windows XP [32 bit], respectively.