Assuming the data is in sheet1, put a formula like =upper(sheet1!a1) in a1 of sheet2. Copy (drag and drop the copy handle is the easiest way) all over (all the cells with serial number). Then edit>copy>paste special>values back to sheet1. You can delete sheet2 afterwards.
Hope this helps.
two days ago i got a list of serial number in excel but the font and size are small because it so small i make it bigger but the problem is how to change the serial number into uppercase format
any tip on using it on microsoft office 2003