Organisations are now investing in HTML5 "which we're still figuring out" and so could be sowing the seeds of a set of future compatibility issues. "There are lessons that they can't learn yet," Mr Jackson suggested.
In some cases, Microsoft has been able to address issues. For example, applications written in Visual Basic 4 generally try to write to restricted locations (ie, they assume the user has administrator privileges) but they still work in current versions of Windows because that issue was "fixed for free" by microsoft, he said.
Organisations should consider hidden dependencies, he said. For instance there is a lot of Visual Basic 6 code in use, and while it is fully supported in Windows 7, support for the VB6 development environment ended years ago. So how will you fix any bugs, especially those with security implications?
Mr Jackson also sees some organisations decide to standardise on a specific releases of software such as Java to ensure application compatibility, but he says missing out on subsequent security updates leaves them open to real risks.
Disclosure: The writer attended Tech.Ed as the guest of Microsoft.