Excel Auto FIll Issue

Hey All,

I have an issues, thus I am writing to you guys, that is really bothering me. I have a user who is using Excel XP and when they have Excel auto fill numbers it doesn't add correctly. They are trying to work with numbers starting with 312.1, 312.2, 312.3 and so on. When they perform the auto fill it works for about ~17 cells then gives us 313.699999999999. Every number after that is shown in this fashion. If you go to the cell that mucks up and auto fill from a couple numbers up it works for 15 cells. I formatted his cells to only show 1 decimal place but in the formula bar you still see this strange number. I am able to get this error with all numbers containing decimals but some take longer then others to appear.

I tried finding a pattern but it does not seem like this is one. "Larger" numbers (300's) all do it around ~17 cells. "Smaller" numbers (1.1, 1.2, 1.3) shows up around ~38 cells. An anomaly of 200's (200.1, 200.2, 200.3) doesn't show up until about ~108 cells.... Whole numbers work fine. Numbers with 2 decimals show up later (~59 cells).

I can reproduce this issue in Excel XP, 2003, 2010 and tried this on multiple computers (all running Widows XP SP3 32bit).

I have no idea what is causing this issue. I have no idea if this is a common issue. Can this be fixed and how?