Legacy software modernisation, without stopping work

Signs your legacy application needs modernising

Old software is not a problem in itself. Plenty of 20-year-old applications still do their job. It becomes a problem when the risk of keeping it grows faster than the cost of replacing it. The usual signs:

• It runs on one particular PC or server that nobody wants to switch off.
• Staff use it over remote desktop because it cannot run anywhere else.
• It cannot be used from a phone, a tablet or outside the office network.
• Reports are exported to Excel before anyone can actually use them.
• Your cyber insurer or a Cyber Essentials assessment asks about unsupported software.
• The developer who built it has retired or the company has gone, and the source code may not even be to hand.

Windows 10 end of support and older applications

Microsoft ended support for Windows 10 on 14 October 2025: the PCs keep working, but they no longer receive security updates unless enrolled in Extended Security Updates. For home users that runs to 12 October 2027. Organisations can buy up to three years, paid year by year, with the price doubling each year. It buys time; it does not solve the problem.

The UK's National Cyber Security Centre is blunt: the only fully effective way to mitigate the risk of an obsolete product is to stop using it. Until then it recommends isolating it, keeping sensitive data away from it and planning the migration. For Cyber Essentials, guidance from IASME, which runs the scheme's certification for the NCSC, says unsupported software must be removed or moved to a separately managed, segregated part of the network outside the certification scope.

Often the operating system can be upgraded but the application is what holds things back: it needs an old database driver, a 32-bit component or a printer setup that nobody dares touch.

MS Access to web app, VB6 and Delphi migration

Each technology has its own pitfalls, and most of the work lies in recovering the business rules buried in the code:

• Microsoft Access: a database file is capped at 2 GB. Many Access systems are split into a front end on each PC and a back end on a network share, and they slow down or corrupt as users grow. A sensible first step can be moving the tables to SQL Server or PostgreSQL; the forms, queries and VBA modules then become web screens and server-side rules.
• Visual Basic 6: Microsoft still supports the VB6 runtime on Windows 11 and recent Windows Server, but the development environment has been unsupported since 8 April 2008. The application may run for years yet, but changing it safely gets harder every year.
• Delphi: older applications often depend on third-party components or local database formats that are no longer maintained, which makes them hard to compile on modern tools.
• Early web applications: old PHP or ASP versions, frameworks without security updates, and servers nobody can rebuild if they fail.

Legacy modernisation options: from rehosting to rebuild

There is no single right answer. The choice depends on how good the current logic is, how much it needs to change and how much risk you can take on while it happens. A software code audit is often the cheapest way to decide.

How we would modernise without stopping the business

We start from the running system and its data rather than from old documentation, which is rarely current. Each rule recovered from the code is confirmed with the people who use it, and before each module is switched over, old and new are run on the same data until the outputs match.

You see a working demo every two weeks, the project has one fixed price, and the new code lives in a repository in your company's name, so this does not happen again. The full method is on our page about fixed price software development, and market reference figures are in the guide on how much custom software costs.