Same query different result

[kutlesh]

I have this query

SELECT 

InputTable.Year, 
AddressBook.Summary, 
AddressBook.ID1, 
First(AddressBook.TypeOfSchool) AS FirstOfTypeOfSchool, 
Max(IIf([TypeOfSchool]="First Degree","Second Degree",[TypeOfSchool])) AS TypeOfSchool, 
AddressBook.Science, 
Count(InputTable.Sex) AS CountOfSex, 
Sum(IIf(([YearFinished]-[FirstYearEnrolled])<=([YearsLong]-Int([FirstSemester]/2)),1,0)) AS WithingRange

FROM InputTable 
INNER JOIN AddressBook 
ON (InputTable.Code = AddressBook.Code) AND (InputTable.SubCode = AddressBook.SubCode)
GROUP BY 
InputTable.Year, 
AddressBook.Summary, 
AddressBook.ID1, 
AddressBook.Science;

A year ago, I had two MS Access installations. I think the old Access got broken and then it needed to reinstalled.
A year ago, that same query was listing one result. However when I run it now, it produces different result.

Could there be some issue with MS Access, going from lower to upper version, or having two Access installed on the same machine?

Something fishy in

Sum(IIf(([YearFinished]-[FirstYearEnrolled])<=([YearsLong]-Int([FirstSemester]/2)),1,0)) AS WithingRange

Simply said, this query should split the input table data in two sets, one where students finished school within the possible longevity of the school and second, students needed more years to finish the school than the school lasts.

So a year ago, i got say 2500, now when i run it i get 2000 for students finished within the longevity of the school, and those 500 go into the set for student who didn't finish in time.