I have been using Excel 97 to keep track of my finances and one particular file appears to have become corrupted. The last time I added to that file it appeared in a slightly different format. The items listed took up two lines instead of one. I added an item and closed the program. However, now when I try to open the file the following message appears: ‘File format is not valid’. The file is still listed in Windows Explorer as taking up 31kb. Have you any ideas how I may retrieve the file?

It sounds like your Excel spreadsheet is corrupted. This could have happened when you opened the file and it had the peculiarity of the items taking up two lines instead of one. Then when you added some data and saved the document, it saved the Excel spreadsheet in the corrupted state. There are a few things we can try to open the corrupted file. Firstly, try opening the file through Microsoft Word. Sometimes Word will open the file if Excel refuses. Alternatively you will be presented with a screen of garbage characters or Word will also refuse. You may be prompted to install an add-on, so have your Microsoft Office CD handy. A second possible fix is to find a computer running a later version of Excel, say Excel 2000 or, even better, Excel 2002. A later version of Excel may be able to open and fix corrupt files better than earlier versions. If this works, make sure that you save the spreadsheet in an Excel 97 compatible format (otherwise it may default to save in Excel 2000X format and you may not be able to open the spreadsheet in Excel 97). A final, and more expensive, option is to try a commercial Excel recovery package. You can find a list of some of these packages at directory.google.com/Top/Computers/Software/Spreadsheets/Excel/Data_Recovery/. Be aware that these do cost money and there is no guarantee they will be able to fix the problem with your Excel file. If you cannot fix the problem, short of purchasing a commercial recovery package, I would just cut your losses and start the spreadsheet from scratch. However, before investing too much time in creating the new file, run a test spreadsheet to be sure that the earlier problem is not endemic to your software.