Convert Hh:mm:ss To Seconds

Hi

This is my 1st post so please be gentle

I am running an Access Database for a large uk companys call centre.. I use many diffrent systems which allow me to show our centres productivity...

I have hit a wall

When i first developed the DB i used the time formatting hh:mm:ss but later down the line i found if you *the time by 86400 it converts the hh:mm:ss into a workable seconds format....

One of my old extracts that i feedinto the DB are in the old format therefor i do this calculation within an access query which *the time by 86400

however i have found an probelm.. if the time is over 24hrs it seems to double the time there or there abouts in seeconds

example

01/01/1900 01:42:00 which is basically 25 hrs should be around 92520 seconds

when is do this calculation in an access query it is coming out 178920 all the other times are correct so this rules out how i link 2 querys ....

any ideas???