I believe Excel 2007 has moved beyond this limit, but if you are using an earlier version, then column IV is the limit, at 256 columns.
There may be workarounds, but they may not be pretty. For example, can you create more worksheets and use those?
I have a rather big spreadsheet (many columns)
I was adding some additional information and I cannot add any more columns. It stops at IV. That is not a 4, it is the letters IV.
Am I doing something wrong?