you can use the find and replace function with dates. Just enter 200 in the
find and 2006 in the replace. Otherwise you will have to use text functions
because 4/25/200 is not a date as far as excel is concerned.
If you want a function something like this will work
=IF(ISTEXT(A1),DATE(2006,LEFT(A1,FIND("/",A1)-1),MID(A1,FIND("/",A1)+1,FIND("/",A1,1+FIND("/",A1))-FIND("/",A1)-1)),DATE(2006,MONTH(A1),DAY(A1)))
You need this longer version of the formula already posted because 4/25/200
is not a date as far as excel is concerned. It treats anything before 1900
and after 9999 as text.