Old .doc and .xls files: what converting really changes and how to check a whole batch

What Compatibility Mode is telling you

When Word or Excel opens a file made in an older version, the title bar says Compatibility Mode. Microsoft explains that it temporarily disables newer features so people on the earlier version can still work on the file, and keeps the existing layout. Converting removes that restriction. For Word, File, Info, Convert converts the document without saving a copy, and Save As makes a separate one. Excel works the same way: convert replaces the original with a current-format copy, while Save As keeps the old file.

The practical rule for a batch follows directly: never use the in-place convert on originals. Always produce a copy.

What can change, and what Microsoft says about it

Microsoft's pages are cautious. They do not list every layout change; the Word page says only that converting clears the compatibility options so the layout follows current behaviour. Both the Word and Excel pages tell you to keep a backup of the original and to verify the content or layout of the converted file for changes. On size, Excel's documentation says data beyond 65,536 rows by 256 columns is lost when a workbook is saved in the old format, while its specifications page gives the current worksheet limit as 1,048,576 rows by 16,384 columns.

Macros need a decision. Both pages say files with macros can be saved in the macro-enabled formats, .docm and .xlsm, and that the Developer tab lists macros. Because Microsoft directs macro files to those formats, macro files must be identified first and handled separately, not converted along with everything else.

• No itemised list of layout differences is published; the checks below are what we propose, not a vendor guarantee.
• The Excel documentation referred to here is marked as retired because the versions it covered are out of support.

Build the inventory before converting anything

Count the files by type, size and folder depth. Identify which contain macros, which are password-protected and which cannot be opened at all. Record each file's checksum so you can show later that no original changed. Decide the target format for each type and what happens to macro files. This list is the contract: at the end, every file on it must be converted or listed as an exception with a reason.

Check the result in a way that finds differences

For a sample of converted files, compare with the originals. For a Word file, compare the page count, measuring the original and the converted file in the same application, version and settings so that a difference in the application is not mistaken for a difference in the file, and look at pages with tables, images and headers. For an Excel file, compare the number of sheets, the number of formulas and a few key totals. List every difference found rather than judging it acceptable on the spot.

Then compare the checksums of the originals before and after the job. A conversion that touched an original is a failure however good the new files look.

• Inventory count = converted files + files listed as exceptions.
• Every original has the same checksum before and after.
• Page counts for an original and its converted file are measured in the same application, version and settings.
• The sample report lists each difference, not just a pass or fail mark.

Where the paid job fits, and where it does not

Up to 300 old .doc and .xls files in one folder tree can be converted as a one-off job from £295 (an untested proposal). Converted copies go in a parallel folder structure, and files with macros become .docm or .xlsm only if you agree. The job is accepted by the inventory reconciliation, a sample that opens in the named application without a repair prompt or compatibility label, the page, sheet and formula comparisons measured in that same application, and unchanged originals. The conversion tool and the checking application are named, with versions, in the written scope. Payment follows your sign-off. It does not edit content, repair formulas, rewrite macros or advise on whether originals may be deleted.

A whole archive that also contains scans and needs renaming is a larger scope, covered by the archive project. The first enquiry needs counts and types, never the files. Files with personal data are not covered, and work starts only after a secure way to hand the files over has been agreed in writing; no upload portal exists yet.