When a new service pack is released, Microsoft will provide either 12 or
24 months of support for the previous service pack

A lot of msft suite is going to expire i.e. "go out of support" completely in 2010 - 2011 time frame

by next year sqlserver 2005 is pretty much a goner!!

http://support.microsoft.com/lifecycle/?p1=2855

..so is windows 2003..starting this july!!
http://support.microsoft.com/lifecycle/?p1=3198

..visual studio 2005..gone by Apr '11
http://support.microsoft.com/lifecycle/?p1=3041